Anode and battery

ABSTRACT

An anode and battery including the anode capable of improving the cycle characteristics while securing the input and output characteristics is provided. The battery includes a cathode, an anode, and an electrolytic solution. The anode includes an anode active material layer on an anode current collector, wherein the anode active material layer includes an anode active material capable of intercalating and deintercalating an electrode reactant, wherein a thickness of the anode active material layer ranges from 60 μm to 120 μm, and wherein the anode active material includes a carbon material and at least part of a surface is covered by a covering, the covering including at least one of an alkali metal salt and an alkali earth metal salt.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/141,588, filed on Jun. 18, 2008, which claims priority toJapanese Patent Application JP 2007-178365 filed in the Japanese PatentOffice on Jul. 6, 2007, the entire contents of which being incorporatedherein by reference.

BACKGROUND

The present application relates to an anode and a battery including theanode.

In recent years, portable electronic devices such as combination cameras(videotape recorder), mobile phones, and notebook personal computershave been widely used, and it is strongly demanded to reduce their sizeand weight and to achieve their long life. Accordingly, as a powersource for the portable electronic devices, a battery, in particular alight-weight secondary batter capable of providing a high energy densityhas been developed. Specially, a secondary battery using intercalationand deintercalation of lithium for charge and discharge reaction(so-called lithium ion secondary battery) is extremely prospective,since such a secondary battery provides a higher energy density comparedto a lead battery and a nickel cadmium battery.

The lithium ion secondary battery has a cathode, an anode, and anelectrolytic solution. The anode has an anode active material layer onan anode current collector. As an anode active material in the anodeactive material layer, a carbon material such as graphite has beenwidely used.

In the case that the carbon material is used as an anode activematerial, further improvement of the battery capacity is an issue, sincethe battery capacity already reaches the level close to the theoreticalcapacity. To solve such an issue, the following technique has beenproposed (for example, refer to Japanese Unexamined Patent ApplicationPublication No. 09-204936). In the technique, by increasing thethickness of the anode active material layer, the occupancy ratio of theanode active material layer in the battery is relatively increased tothe occupancy ratios of the anode current collector and the separator.In the specification, such a technique in which the thickness of theanode active material layer is intentionally increased to achieve a highcapacity is referred to as “thickening of the anode active materiallayer.”

The technique of thickening of the anode active material layer is usefulto improve the battery capacity. On the other hand, the technique causesa new issue. Specifically, when design is made so that the thickness ofthe anode active material layer is increased while the material and thedensity thereof are maintained as before under a constant batteryvolume, the occupancy ratio of the anode current collector in thebattery is decreased, and the anode active material amount formed perunit area of the anode current collector is increased. Thus, when thesame electric capacity is charged and discharged, the current density ofthe anode is relatively increased. Therefore, in the anode,intercalation (insertion) and deintercalation (extraction) of lithiumions are not sufficiently generated. In some cases, lithium isprecipitated, becomes a dendrite, and loses its activity. In the result,input and output characteristics of the lithium ions in charge anddischarge are lowered. Further, when charge and discharge are repeated,the discharge capacity is largely lowered, and thus the cyclecharacteristics are also lowered.

The foregoing issue similarly occurs in the case that the volume densityof the anode active material layer is increased to obtain a high batterycapacity as well, in addition to the case that thickening of the anodeactive material layer is implemented. This is because when the volumedensity of the anode active material layer is increased, gaps where thelithium ions are moved become small, and thus the transfer rate of thelithium ions in charge becomes slow. In the specification, such atechnique to intentionally increase the volume density of the anodeactive material layer to achieve a high capacity is referred to as“increase of the volume density of the anode active material layer.”

In recent years, as the high performance and the multi functions of theportable electronic devices are developed, further improvement of thebattery capacity is demanded. Thus, it has been considered to usesilicon, tin or the like instead of the carbon material (for example,refer to U.S. Pat. No. 4,950,566). Since the theoretical capacity ofsilicon (4199 mAh/g) and the theoretical capacity of tin (994 mAh/g) aresignificantly higher than the theoretical capacity of graphite (372mAh/g), it is prospected that the battery capacity is thereby highlyimproved.

When silicon or the like with the high theoretical capacity is used asan anode active material, the battery capacity is improved. On the otherhand, when lithium ions are intercalated, the anode active materialbecomes highly activated. Thus, the electrolytic solution is easilydecomposed. Accordingly, when charge and discharge are repeated, thecycle characteristics are lowered as in the case of thickening of theanode active material layer and increase of the volume density of theanode active material layer with the use of the carbon material as ananode active material.

To improve the input and output characteristics and the cyclecharacteristics, various techniques have been already proposed.Specifically, a technique to provide a carbon shell added with an alkalimetal element or an alkali earth metal element on a crystalline graphitecore in the case that a carbon material is used as an anode activematerial (for example, refer to Japanese Unexamined Patent ApplicationPublication No. 2000-164218), a technique to provide a surface treatmentlayer containing a coating element-containing compound such as hydroxideand an electrical conductor on the surface of the anode active material(for example, refer to Japanese Unexamined Patent ApplicationPublication No. 2003-100296), and a technique to provide a thin filmmade of a metal or a metal oxide on the surface of the anode activematerial (for example, refer to Japanese Unexamined Patent ApplicationPublication No. 2003-249219) are known.

SUMMARY

The high performance and the multi functions of the recent portableelectronic devices tend to be increasingly developed. Thus, furtherimprovement of the input and output characteristics and the cyclecharacteristics of the secondary batteries is aspired. In particular, inthe case that a carbon material is used as an anode active material, itis important to improve the input and output characteristics and thecycle characteristics even if thickening of the anode active materiallayer and increase of the volume density of the anode active materiallayer are implemented. Meanwhile, in the case that silicon or the likewith the high theoretical capacity is used as an anode active material,it is important that the cycle characteristics are improved while theinput and output characteristics are maintained.

In view of the foregoing, it is desirable to provide an anode materialcapable of improving the cycle characteristics while securing the inputand output characteristics, an anode and a battery, and methods ofmanufacturing them.

According to an embodiment, an anode and battery including the anodecapable of improving the cycle characteristics while securing the inputand output characteristics is provided. The battery includes a cathode,an anode, and an electrolytic solution. The anode includes an anodeactive material layer on an anode current collector, wherein the anodeactive material layer includes an anode active material capable ofintercalating and deintercalating an electrode reactant, wherein athickness of the anode active material layer ranges from 60 μm to 120μm, and wherein the anode active material includes a carbon material andat least part of a surface is covered by a covering, the coveringincluding at least one of an alkali metal salt and an alkali earth metalsalt.

According to an embodiment, there is provided an anode materialincluding a plurality of covering particles on a surface of an anodeactive material capable of intercalating and deintercalating anelectrode reactant, in which the plurality of covering particles containat least one of an alkali metal salt and an alkali earth metal salt.According to an embodiment, there is provided a method of manufacturingan anode material having a plurality of covering particles on a surfaceof an anode active material capable of intercalating and deintercalatingan electrode reactant, in which at least one of an alkali metal salt andan alkali earth metal salt is dissolved and then precipitated on thesurface of the anode active material to form the plurality of coveringparticles.

According to an embodiment, there is provided an anode including ananode active material layer on an anode current collector, in which theanode active material layer contains an anode material having aplurality of covering particles on a surface of an anode active materialcapable of intercalating and deintercalating an electrode reactant, andthe plurality of covering particles contain at least one of an alkalimetal salt and an alkali earth metal salt. According to an embodiment,there is provided a method of manufacturing an anode having an anodeactive material layer on an anode current collector in which the anodeactive material layer contains an anode material having a plurality ofcovering particles on a surface of an anode active material capable ofintercalating and deintercalating an electrode reactant. At least one ofan alkali metal salt and an alkali earth metal salt is dissolved andthen precipitated on the surface of the anode active material to formthe plurality of covering particles.

According to an embodiment, there is provided a battery including acathode, an anode, and an electrolytic solution. The anode has an anodeactive material layer on an anode current collector, the anode activematerial layer contains an anode material having a plurality of coveringparticles on a surface of an anode active material capable ofintercalating and deintercalating an electrode reactant, and theplurality of covering particles contain at least one of an alkali metalsalt and an alkali earth metal salt. According to an embodiment, thereis provided a method of manufacturing a battery having a cathode, ananode, and an electrolytic solution, in which the anode has an anodeactive material layer on an anode current collector, and the anodeactive material layer contains an anode material having a plurality ofcovering particles on a surface of an anode active material capable ofintercalating and deintercalating an electrode reactant. At least one ofan alkali metal salt and an alkali earth metal salt is dissolved andthen precipitated on the surface of the anode active material to formthe plurality of covering particles.

According to the anode material and the method of manufacturing it ofthe embodiments, the plurality of covering particles containing at leastone of the alkali metal salt and the alkali earth metal salt are formedon the surface of the anode active material capable of intercalating anddeintercalating the electrode reactant. Thus, intercalation andde-intercalation of the electrode reactant are easily generated in theanode active material, and the chemical stability of the anode activematerial is improved. Thereby, according to the anode material, theanode or the battery using the method of manufacturing the anodematerial, or the method of manufacturing the anode or the battery, theelectrode reactant is smoothly intercalated and deintercalated inelectrode reaction, and decomposition reaction of the electrolyticsolution is inhibited. Thus, the cycle characteristics may be improvedwhile the input and output characteristics are secured.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross section schematically showing a structure of an anodematerial according to a first embodiment;

FIG. 2 is a cross section showing a structure of a first battery;

FIG. 3 is a cross section showing an enlarged part of the spirally woundelectrode body shown in FIG. 2;

FIG. 4 is a cross section schematically showing a structure of an anodematerial used for the first battery before the initial charge;

FIG. 5 is a cross section schematically showing a structure of the anodematerial used for the first battery after the initial charge;

FIG. 6 is an exploded perspective view showing a structure of a secondbattery;

FIG. 7 is a cross section showing a structure taken along line VII-VIIof the spirally wound electrode body shown in FIG. 6;

FIG. 8 is a cross section schematically showing a structure of an anodematerial used for the second battery before the initial charge;

FIG. 9 is a cross section schematically showing a structure of the anodematerial used for the second battery after the initial charge;

FIG. 10 is a diagram showing a correlation between a ratio of aplurality of covering particles to an anode active material and aninitial charge and discharge efficiency/a discharge capacity retentionratio (anode active material: MCMB);

FIG. 11 is a diagram showing the analytical result of a SnCoC-containingmaterial by XPS; and

FIG. 12 is a diagram showing a correlation between a ratio of aplurality of covering particles to an anode active material and aninitial charge and discharge efficiency/a discharge capacity retentionratio (anode active material: SnCoC-containing material).

DETAILED DESCRIPTION

Embodiments will be hereinafter described in detail with reference tothe drawings.

First Embodiment

FIG. 1 schematically shows a cross sectional structure of an anodematerial according to a first embodiment. An anode material 10 is used,for example, for an electrochemical device including an anode such as abattery. The anode material 10 has an anode active material 1 capable ofintercalating and deintercalating an electrode reactant and a pluralityof covering particles 2 provided thereon.

The anode active material 1 contains one or more materials capable ofintercalating and deintercalating an electrode reactant, and forexample, contains a carbon material. In the carbon material, a change incrystal structure in electrode reaction (in intercalation anddeintercalation of the electrode reactant) is extremely small, andthereby a high energy density is obtained. The type of electrodereactant may be voluntarily selected. For example, in the case that theanode material is used for a lithium ion secondary battery, theelectrode reactant is lithium.

As the carbon material, for example, graphite, non-graphitizable carbon,graphitizable carbon and the like are cited. More specifically,pyrolytic carbons, coke, glassy carbon fiber, an organic polymercompound fired body, activated carbon, carbon black or the like iscited. Of the foregoing, the coke includes pitch coke, needle coke,petroleum coke and the like. The organic polymer compound fired body isobtained by firing and carbonizing a phenol resin, a furan resin or thelike at an appropriate temperature. One of the carbon materials may beused singly, or a plurality thereof may be used by mixture. The shape ofthe carbon material may be any of a fibrous shape, a spherical shape, agranular shape, and a scale-like shape.

Specially, as the carbon material, graphite is preferable, since theelectrochemical equivalent is large and thus a higher energy density isthereby obtained. In particular, natural graphite is preferable toartificial graphite, since a higher energy density is thereby obtained.

As the graphite, graphite in which the lattice spacing d₀₀₂ in theC-axis direction measured by X-ray diffraction method is 0.340 nm orless is preferable, and graphite in which the lattice spacing d₀₀₂ inthe C-axis direction measured by X-ray diffraction method is in therange from 0.335 nm to less than 0.338 nm is more preferable, since ahigher energy density is thereby obtained.

As the non-graphitizable carbon, the non-graphitizable carbon in whichthe lattice spacing d₀₀₂ in the C-axis direction measured by X-raydiffraction method is 0.37 nm or more, the real density is less than1.70 g/cm³, and no exothermic peak is observed at 700 deg C or morebased on Differential Thermal Analysis (DTA) in the air is preferable,since a higher energy density is thereby obtained.

The foregoing lattice spacing d₀₀₂ may be measured by X-ray diffractionmethod in which, for example, CuKα-ray and high purity silicon arerespectively used as an X-ray and a standard material.

Other conditions such as the specific surface area of the carbonmaterial may be voluntarily set according to the usage purpose, thedemanded performance and the like of the anode material.

The plurality of covering particles 2 contain at least one of an alkalimetal salt and an alkali earth metal salt. When the anode material hasthe covering particles 2, intercalation and de-intercalation of theelectrode reactant are easily generated in the anode active material 1,and the chemical stability of the anode active material 1 is improved.The former action contributes to easy electrode reaction even if theanode current density of the anode is increased. The latter actioncontributes to hard reaction between the anode active material 1 andother material even if the anode active material 1 becomes highly activein electrode reaction. Such other material is, for example, anelectrolytic solution in the case that the anode material is used forthe lithium ion secondary battery.

The type of alkali metal is not particularly limited as long as analkali metal is a Group 1A element in the short period periodic table.Specially, lithium, sodium, or potassium is preferable. The type ofalkali earth metal is not particularly limited as long as an alkaliearth metal is a Group 2A element in the short period periodic table.Specially, magnesium or calcium is preferable, since both the elementsprovide sufficient effects. The alkali metal and the alkali earth metalmay be used singly, or a plurality thereof may be used by mixture.

The types of alkali metal salt and alkali earth metal salt are notparticularly limited. Specially, a chloride salt, a carbonate, or ahydrosulfate is preferable, since sufficient effects are therebyobtained. Such a chloride salt and the like may be used singly, or aplurality thereof may be used by mixture.

Specific examples of the alkali metal salt are as follows. As thechloride salt, lithium chloride, sodium chloride, potassium chloride orthe like is cited. As the carbonate, lithium carbonate, sodiumcarbonate, potassium carbonate or the like is cited. As thehydrosulfate, lithium sulfate (Li₂SO₄), sodium sulfate (Na₂SO₄),potassium sulfate (K₂SO₄) or the like is cited.

Of the alkali earth metal salts, as the carbonate, for example,magnesium carbonate, calcium carbonate and the like are cited.

It is enough that the plurality of covering particles 2 exist on atleast part of the surface of the anode active material 1. That is, theplurality of covering particles 2 may exist on part of the surface ofthe anode active material 1 or on all of the surface of the anode activematerial 1. In this case, it is possible that the plurality of coveringparticles 2 form an aggregation and thereby the film-like aggregationcovers at least part of the surface of the anode active material 1. Itis needless to say that the foregoing aspects of the covering particles2 may be mixed. FIG. 1 shows a case that the plurality of coveringparticles 2 form a single layer structure. However, the plurality ofcovering particles 2 may be layered on the anode active material 1 toform a lamination structure. In this case, the total thickness(so-called film thickness) of the covering particles 2 may be uniform ormay be changed.

The ratio of the plurality of covering particles 2 to the anode activematerial 1 may be voluntarily set, but is preferably in the range from0.1 wt % to 10 wt %. Thereby, intercalation and de-intercalation of theelectrode reactant are easily generated, and the chemical stability ofthe anode active material 1 is further improved. More specifically, ifthe ratio is smaller than 0.1 wt %, the number of the covering particles2 is excessively small, and in the result there is a possibility thatintercalation and de-intercalation of the electrode reactant are notsufficiently generated and the chemical stability of the anode activematerial 1 is not sufficiently improved. Meanwhile, if the ratio islarger than 10 wt %, the number of the covering particles 2 isexcessively large and the internal resistance is increased, and in theresult there is a possibility that sufficient input and outputcharacteristics are not obtained. The foregoing “ratio of the pluralityof covering particles 2 to the anode active material 1” indicates theratio of the weight of the plurality of covering particles 2 to theweight of the anode active material 1, and is expressed as (weight ofthe plurality of covering particles 2/weight of the anode activematerial 1)×100.

The ratio of the plurality of covering particles 2 to the anode activematerial 1 may be calculated, for example, based on the weight of theanode active material 1 on which the covering particles 2 are providedand the weight of the anode active material 1 measured after thecovering particles 2 are dissolved and removed in the case that thecovering particles 2 show the solubility.

To easily explain the structure of the anode active material 1 and theplurality of covering particles 2, FIG. 1 schematically shows thestructure. The shape, the particle diameter, the number and the like ofthe anode active material 1 and the covering particles 2 may bevoluntarily set, and are not limited to the aspect shown in FIG. 1.

The structure of the anode material 10 shown in FIG. 1 (structure inwhich the plurality of covering particles 2 exist on the surface of theanode active material 1) may be identified by element analysis (depthdirection analysis) with the use of, for example, X-ray ElectronSpectroscopy for Chemical Analysis (ESCA). When the foregoing elementanalysis by ESCA is performed, some amount of impurity and the like maybe mixed in the anode active material 1 or the covering particles 2. Inthis case, the structure of the anode material 10 may be also identifiedby ESCA. This is because in the element analysis by ESCA, the carbonmaterial is supposed to be measured as a rich region for the anodeactive material 1, and the alkali metal salt and the like are supposedto be measured as a rich region for the covering particles 2.

The anode material may be manufactured by, for example, by the followingprocedure.

First, a treated solution in which at least one powder of the alkalimetal salt and the alkali earth metal salt (hereinafter also simplyreferred to as “alkali metal salt and the like”) is dissolved isprepared. The type of solvent is not particularly limited. However, inthe case that the anode material is used for a nonaqueous solvent-basedelectrochemical device, to prevent the covering particles 2 from beingdissolved and separated from the anode active material 1, water is morepreferably used as a solvent than a nonaqueous solvent. Subsequently,the anode active material 1 is dipped in the treated solution. Afterthat, the treated solution is agitated and disperse the anode activematerial 1. The conditions such as an agitating speed and agitating timemay be voluntarily set. Finally, after the solution in which the anodeactive material 1 is dipped is filtered, the anode active material 1 isdried in the vacuum environment at high temperature to precipitate thealkali metal salt and the like dissolved in the solution on the surfaceof the anode active material 1. The conditions such as a degree ofvacuum (pressure), temperature, and drying time may be voluntarily set.Thereby, the plurality of covering particles 2 are formed on the surfaceof the anode active material 1, and accordingly the anode material isfabricated.

When the anode material is formed, for example, by adjusting thedissolution amount (weight) of the alkali metal salt and the like in thetreated solution and the input amount (weight) of the anode activematerial 1 into the treated solution, the ratio of the plurality ofcovering particles 2 to the anode active material 1 may be set to adesired value.

When the treated solution is filtered, there is a possibility that partof the alkali metal salt and the like remains on the wall face of thevessel containing the treated solution and an error is generated betweenthe dissolution amount and the precipitation amount of the alkali metalsalt and the like. However, if the treated solution in which the anodeactive material 1 is dipped is sufficiently agitated and then filtered,mpst of the alkali metal salt and the like dissolved in the treatedsolution is transferred to and fixed on the surface of the anode activematerial 1, and thus the foregoing error becomes extremely small.Accordingly, by the foregoing method, the ratio of the plurality ofcovering particles 2 to the anode active material 1 may be preciselyset.

According to the anode material and the method of manufacturing it ofthis embodiment, the anode active material 1 is formed from the carbonmaterial capable of intercalating and deintercalating the electrodereactant, and the plurality of covering particles 2 containing at leastone of the alkali metal salt and the alkali earth metal salt are formedon the surface of the anode active material 1. Thus, compared to a casethat the plurality of covering particles 2 are not formed, the followingadvantages are obtained. Firstly, since intercalation andde-intercalation of the electrode reactant are easily generated in theanode active material 1, electrode reaction is easily generated even inthe case that the current density of the anode is increased. Secondly,since the chemical stability of the anode active material 1 is improved,the anode active material 1 is hardly reacted with other material evenin the case that the anode active material 1 becomes highly reactive inelectrode reaction. Therefore, the anode material and the method ofmanufacturing it of this embodiment contributes to improvement of theperformance of the electrochemical device using the anode material.

In this case, since the plurality of covering particles 2 are formed bysimple treatment in which the alkali metal salt and the like aredissolved and then precipitated, the plurality of covering particles 2may be simply and stably formed.

In particular, when the anode active material 1 contains naturalgraphite as a carbon material, or the ratio of the plurality of coveringparticles 2 to the anode active material 1 is in the range from 0.1 wt %to 10 wt %, higher effects are obtained.

Next, a description will be hereinafter given of a usage example of theforegoing anode material. As an example of the electrochemical devicesincluding the anode, batteries are herein taken. The anode material isused for the batteries as follows.

First Battery

FIG. 2 shows a cross sectional structure of a first battery. The batteryis a lithium ion secondary battery in which the anode capacity isexpressed based on intercalation and deintercalation of lithium as anelectrode reactant.

In the secondary battery, a spirally wound electrode body 20 in which acathode 21 and an anode 22 are layered with a separator 23 in betweenand spirally wound and a pair of insulating plates 12 and 13 arecontained in a battery can 11 in the shape of an approximately hollowcylinder. The battery can 11 is made of, for example, iron plated bynickel. One end of the battery can 11 is closed, and the other endthereof is opened. The pair of insulating plates 12 and 13 isrespectively arranged perpendicular to the winding periphery face, sothat the spirally wound electrode body 20 is sandwiched between theinsulating plates 12 and 13. The battery structure using the cylindricalbattery can 11 is called cylindrical type.

At the open end of the battery can 11, a battery cover 14, and a safetyvalve mechanism 15 and a Positive Temperature Coefficient (PTC) device16 provided inside the battery cover 14 are attached by being caulkedwith a gasket 17. Inside of the battery can 11 is thereby hermeticallyclosed. The battery cover 14 is, for example, made of a material similarto that of the battery can 11. The safety valve mechanism 15 iselectrically connected to the battery cover 14 through the PTC device16. If the internal pressure of the battery becomes a certain level ormore due to internal short circuit, external heating or the like, a diskplate 15A flips to cut the electrical connection between the batterycover 14 and the spirally wound electrode body 20. When temperaturerises, the PTC device 16 limits a current by increasing the resistancevalue to prevent abnormal heat generation by a large current. The gasket17 is made of, for example, an insulating material and its surface iscoated with asphalt.

A center pin 24 may be inserted in the center of the spirally woundelectrode body 20. In the spirally wound electrode body 20, a cathodelead 25 made of aluminum or the like is connected to the cathode 21, andan anode lead 26 made of nickel or the like is connected to the anode22. The cathode lead 25 is electrically connected to the battery cover14 by being welded to the safety valve mechanism 15. The anode lead 26is welded and electrically connected to the battery can 11.

FIG. 3 shows an enlarged part of the spirally wound electrode body 20shown in FIG. 2. The cathode 21 has a structure in which, for example, acathode active material layer 21B is provided on the both faces of acathode current collector 21A having a pair of opposed faces. Thecathode active material layer 21B may be provided on only a single faceof the cathode current collector 21A.

The cathode current collector 21A is made of, for example, a metalmaterial such as aluminum, nickel, and stainless. The cathode activematerial layer 21B contains as a cathode active material, for example,one or more materials capable of intercalating and deintercalatinglithium as an electrode reactant. The cathode active material layer 21Bmay contain an electrical conductor, a binder and the like according toneeds.

As the material capable of intercalating and deintercalating lithium, alithium-containing compound is preferable, since thereby a high energydensity is obtained. As the lithium-containing compound, for example, acomplex oxide containing lithium and a transition metal element or aphosphate compound containing lithium and a transition metal element iscited. In particular, a compound containing at least one selected fromthe group consisting of cobalt, nickel, manganese, and iron as atransition metal element is preferable, since thereby a higher voltageis obtained. The chemical formula thereof is expressed by, for example,Li_(x)M1O₂ or Li_(y)M2PO₄. In the formula, M1 and M2 represent one ormore transition metal elements. Values of x and y vary according tocharge and discharge states of the battery, and are generally in therange of 0.05≦x≦1.10 and 0.05≦y≦1.10.

As the lithium complex oxide containing lithium and a transition metalelement, for example, a lithium-cobalt complex oxide (Li_(x)CoO₂), alithium-nickel complex oxide (Li_(x)NiO₂), a lithium-nickel-cobaltcomplex oxide (Li_(x)Ni_((1-z))Co_(z)O₂ (z<1)), alithium-nickel-cobalt-manganese complex oxide(Li_(x)Ni_(1(1-v-w))Co_(y)Mn_(w)O₂ (v+w<1)), lithium-manganese complexoxide having a spinel structure (LiMn₂O₄) and the like are cited.Specially, the complex oxide containing nickel is preferable, sincethereby a high battery capacity and superior cycle characteristics areobtained. As the phosphate compound containing lithium and a transitionmetal element, for example, lithium-iron phosphate compound (LiFePO₄), alithium-iron-manganese phosphate compound (LiFe_((1-u))Mn_(u)PO₄ (u<1))and the like are cited.

In addition to the foregoing compounds, for example, an oxide such astitanium oxide, vanadium oxide, and manganese dioxide; a disulfide suchas iron disulfide, titanium disulfide, and molybdenum disulfide; achalcogenide such as niobium selenide; and a conductive polymer such aspolyaniline and polythiophene are cited.

As the electrical conductor, for example, a carbon material such asgraphite, carbon black, acetylene black, and Ketjen black are cited.Such a carbon material may be used singly, or a plurality thereof may beused by mixture. The electrical conductor may be a metal material, aconductive polymer or the like as long as the material has theconductivity.

As the binder, for example, a synthetic rubber such as styrene-butadienerubber, fluorinated rubber, and ethylene propylene diene; or a polymermaterial such as polyvinylidene fluoride is cited. One thereof may beused singly, or a plurality thereof may be used by mixture. When thecathode 21 and the anode 22 are spirally wound, the styrene-butadienerubber, the fluorinated rubber or the like having flexibility ispreferable.

The anode 22 has a structure in which an anode active material layer 22Bis provided on the both faces of an anode current collector 22A having apair of opposed faces. The anode active material layer 22B may beprovided only on a single face of the anode current collector 22A.

The anode current collector 22A is preferably made of a metal materialhaving favorable electrochemical stability, electric conductivity, andmechanical strength. As the metal material, for example, copper, nickel,stainless and the like are cited. Specially, copper is preferable, sincethereby high electric conductivity is obtained. The anode activematerial layer 22B contains the foregoing anode material as the materialcapable of intercalating and deintercalating lithium as an electrodereactant. The anode active material layer 22B may contain an electricalconductor, a binder and the like according to needs.

In the secondary battery, it is preferable that the charge capacity ofthe anode active material is larger than the charge capacity of thecathode active material by adjusting the amount of the cathode activematerial and the amount of the anode active material capable ofintercalating and deintercalating lithium.

FIG. 4 and FIG. 5 show cross sectional structures of an anode material220 used for the anode active material layer 22B. Both FIG. 4 and FIG. 5correspond to FIG. 1.

Before the initial charge, as shown in FIG. 4, the anode material 220has a structure similar to that of the foregoing anode material 10, andhas a plurality of covering particles 222 on the surface of an anodeactive material 221 capable of intercalating and deintercalating theelectrode reactant. The structures of the anode active material 221 andthe covering particles 222 are respectively similar to the structures ofthe anode active material 1 and the covering particles 2.

After the initial charge, as shown in FIG. 5, the anode material 220 mayhave a coat 223 covering the plurality of covering particles 222together with the anode active material 221 and the plurality ofcovering particles 222. The coat 223 is formed by irreversible reactionbetween the anode material 220 and an electrolytic solution in theinitial charge in the nonaqueous solvent-based system electrolyticsolution. The coat 223 forms a stable interface that has electrodereactant ion (in this case, lithium ion) conductivity but does not haveelectron conductivity between the anode 22 and the electrolyticsolution. That is, the coat 223 is a so-called Solid ElectrolyteInterface (SEI) film, and contains a decomposition product and the likeof the electrolytic solution. For example, in a lithium ion secondarybattery in which the electrolytic solution contains an ester carbonatesolvent, the coat 223 contains a material having lithium, carbon, oxygenand the like as an element. When the coat 223 exists, intercalation andde-intercalation of lithium ions are easily generated in the anode 22 incharge and discharge.

As shown in FIG. 5, the covering particles 222 are formed separatelyfrom the coat 223. That is, the coat 223 is formed through the initialcharge, while the covering particles 222 have been previously formed onthe surface of the anode active material 221 irrespective of presence ofcharge. The structure of the anode material 220 shown in FIG. 4(structure that the plurality of covering particles 222 exist on thesurface of the anode active material 221) and the structure of the anodematerial 220 shown in FIG. 5 (structure that the plurality of coveringparticles 222 and the coat 223 exist on the surface of the anode activematerial 221) may be identified by element analysis with the use of ESCAas in the foregoing anode material. In the latter case, the coveringparticles 222 and the coat 223 may be partly diffused in each other. Inthis case, the structure of the anode material 220 may be alsoidentified by ESCA. This is because in the element analysis by ESCA, thealkali metal salt and the like are supposed to be measured as a richregion for the covering particles 222, and the foregoing lithium,carbon, oxygen and the like are supposed to be measured as a rich regionfor the coat 223.

The thickness of the anode active material layer 22B is not particularlylimited, but the thickness of the anode active material layer 22B ispreferably a thickness obtained by thickening of the anode activematerial layer (for example, 50 μm or more) to obtain a high batterycapacity, since thereby a sufficient battery capacity is obtained. Inparticular, the foregoing thickness is preferably in the range from 60μm to 120 μm. Thereby, the effect obtained by providing the plurality ofcovering particles 222 on the anode active material 221 becomes higher,specifically, the cycle characteristics are further improved. Morespecifically, if the thickness of the anode active material layer 22B isexcessively thick, intercalation and de-intercalation of lithium ionsmay be hardly generated. The foregoing thickness of the “anode activematerial layer 22B” is a thickness of the anode active material layer22B on a single face side of the anode current collector 22A. That is,in the case where the anode active material layer 22B is provided on theboth faces of the anode current collector 22A, the thickness of theanode active material layer 22B does not indicate the sum of therespective thicknesses of the respective anode active material layers22B on the both sides of the anode current collector 22A, but indicateseach thickness of the anode active material layer 22B on a single side.The definition and the appropriate range of the thickness of the anodeactive material layer 22B are similarly applied to the thickness of thecathode active material layer 21B.

The volume density of the anode active material layer 22B is notparticularly limited, but the volume density of the anode activematerial layer 22B is preferably a volume density obtained by increaseof the volume density of the anode active material layer (for example,1.60 g/cm³ or more) to obtain a high battery capacity, since thereby asufficient battery capacity is obtained. In particular, the volumedensity is preferably in the range from 1.70 g/cm³ to 1.95 g/cm³.Thereby, the cycle characteristics are further improved for the reasonsimilar to that in the case of setting the thickness of the anode activematerial layer 22B to the appropriate value range.

The separator 23 separates the cathode 21 from the anode 22, preventscurrent short circuit due to contact of both electrodes, and passeslithium ions. The separator 23 is made of, for example, a porous filmmade of a synthetic resin such as polytetrafluoroethylene,polypropylene, and polyethylene, or a ceramic porous film. The separator23 may have a structure in which two or more of the foregoing porousfilms are layered. Specially, the porous film made of polyolefin ispreferable, since such a film has a superior short circuit preventiveeffect and improves battery safety by shutdown effect. In particular,polyethylene is preferable, since polyethylene provides shutdown effectat from 100 deg C to 160 deg C and has superior electrochemicalstability. Further, polypropylene is also preferable. In addition, aslong as chemical stability is secured, a resin formed by copolymerizingor blending with polyethylene or polypropylene may be used.

The electrolytic solution as a liquid electrolyte is impregnated in theseparator 23. The electrolytic solution contains a solvent and anelectrolyte salt dissolved in the solvent.

The solvent contains, for example, one or more nonaqueous solvents suchas an organic solvent. The nonaqueous solvents include, for example,ethylene carbonate, propylene carbonate, butylene carbonate, dimethylcarbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone,γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran,2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, methylacetate, methyl propionate, ethyl propionate, acetonitrile,glutaronitrile, adiponitrile, methoxyacetonitrile,3-methoxypropionitrite, N,N-dimethylformamide, N-methylpyrrolidinone,N-methyloxazolidinone, nitromethane, nitroethane, sulfolane, dimethylsulfoxide, trimethyl phosphate, ethylene sulfite,bistrifluoromethylsulfonylimidetrimethylhexyl ammonium and the like arecited. The solvent may be used singly, or a plurality thereof may beused by mixture. Specially, at least one of ethylene carbonate,propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate is preferable. Thereby, a superior battery capacity,superior cycle characteristics, and superior storage characteristics areobtained. In this case, a mixture of a high-viscosity (high dielectricconstant) solvent (for example, specific inductive ∈≧30) such asethylene carbonate and propylene carbonate and a low-viscosity solvent(for example, viscosity≦1 mPa·s) such as dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate is preferable. Thereby, thedissociation property of the electrolyte salt and the ion mobility areimproved, and thus higher effects are obtained.

The solvent preferably contains a cyclic ester carbonate having anunsaturated bond, a chain ester carbonate having a halogen as anelement, a cyclic ester carbonate having a halogen as an element or thelike, since thereby the cycle characteristics are improved. As thecyclic ester carbonate having an unsaturated bond, for example, vinylenecarbonate, vinylethylene carbonate and the like are cited. As the chainester carbonate having a halogen, for example, fluoromethyl methylcarbonate, bis(fluoromethyl) carbonate, difluoromethyl Amethyl carbonateand the like are cited. As the cyclic ester carbonate having a halogen,for example, 4-fluoro-1,3-dioxolane-2-one,4,5-difluoro-1,3-dioxolane-2-one and the like are cited. One thereof maybe used singly, or a plurality thereof may be used by mixture.

The electrolyte salt contains, for example, one or more light metalsalts such as a lithium salt. As the lithium salt, for example, lithiumhexafluorophosphate (LiPF₆), lithium tetrafluoroborate (LiBF₄), lithiumperchlorate (LiClO₄), lithium hexafluoroarsenate (LiAsF_(6,)), lithiumbis(pentafluoroethanesulfonyl)imide (LiN(C₂F₅SO₂)₂), lithiumtrifluoromethanesulfonate (LiCF₃SO₃), lithiumbis(trifluoromethanesulfonyl)imide (LiN(CF₃SO₂)₂), lithiumtris(trifluoromethanesulfonyl)methide (LiC(CF₃SO₂)₃), lithium chloride(LiCl), lithium bromide (LiBr) and the like are cited. Thereby, superiorbattery capacity, superior cycle characteristics, and superior storagecharacteristics are obtained. One thereof may be used singly, or aplurality thereof may be used by mixture. Specially, lithiumhexafluorophosphate is preferable, since the internal resistance islowered, and thus higher effects are obtained.

The content of the electrolyte salt is preferably in the range from 0.3mol/kg to 3.0 mol/kg to the solvent. If the content is out of the range,the ion conductivity is lowered and thus there is a possibility that asufficient battery capacity may not be obtained.

In the secondary battery, when charged, for example, lithium ions aredeintercalated from the cathode 21 and intercalated in the anode 22through the electrolytic solution impregnated in the separator 23.Meanwhile, when discharged, for example, lithium ions are deintercalatedfrom the anode 22 and intercalated in the cathode 21 through theelectrolytic solution impregnated in the separator 23.

The secondary battery may be manufactured, for example, by the followingprocedure.

First, the cathode 21 is formed by forming the cathode active materiallayer 21B on the both faces of the cathode current collector 21A. Inthis case, for example, cathode active material powder, an electricalconductor, and a binder are mixed to prepare a cathode mixture, which isdispersed in a solvent to form paste cathode mixture slurry.Subsequently, the cathode current collector 21A is uniformly coated withthe cathode mixture slurry. After the resultant is dried, the resultantis compression-molded.

Further, the anode 22 is formed by forming the anode active materiallayer 22B on the both faces of the cathode current collector 22A byusing the foregoing anode material. In this case, for example, anodematerial powder, an electrical conductor, and a binder are mixed toprepare an anode mixture, which is dispersed in a solvent to form pasteanode mixture slurry. Subsequently, the anode current collector 22A isuniformly coated with the anode mixture slurry. After the resultant isdried, the resultant is compression-molded.

When the cathode active material layer 21B and the anode active materiallayer 22B are formed, instead of coating the cathode current collector21A and the anode current collector 22A with the cathode mixture slurryand the anode mixture slurry as described above, the cathode mixture andthe anode mixture may be respectively bonded to the cathode currentcollector 21A and the anode current collector 22A.

Next, the cathode lead 25 is attached to the cathode current collector21A by welding, and the anode lead 26 is attached to the anode currentcollector 22A by welding. After that, the cathode 21 and the anode 22are spirally wound with the separator 23 in between to form the spirallywound electrode body 20. Subsequently, the end of the cathode lead 25 iswelded to the safety valve mechanism 15, and the end of the anode lead26 is welded to the battery can 11. After that, while the spirally woundelectrode body 20 is sandwiched between the pair of insulating plates 12and 13, the spirally wound electrode body 20 is contained in the batterycan 11. Subsequently, the electrolytic solution is injected into thebattery can 11, and impregnated in the separator 23. Finally, thebattery cover 14, the safety valve mechanism 15, and the PTC device 16are fixed at the open end of the battery can 11 by being caulked withthe gasket 17. The secondary battery shown in FIG. 2 and FIG. 3 isthereby fabricated.

According to the cylindrical type secondary battery and the method ofmanufacturing it, the anode active material layer 22B of the anode 22contains the anode material 220 having the structure similar to that ofthe anode material described above. Thus, even in the case thatthickening of the anode active material layer 22B and increase of thevolume density of the anode active material layer 22B are implemented toobtain a high battery capacity, lithium ions are smoothly intercalatedand deintercalated in charge and discharge, and decomposition reactionof the electrolytic solution is inhibited. Therefore, while the inputand output characteristics are secured, the cycle characteristics areimproved.

In particular, in the case that the anode active material 221 of theanode material 220 contains a carbon material, the input and outputcharacteristics tend to be lowered in the case of thickening of theanode active material layer 22B and increase of the volume density ofthe anode active material layer 22B are implemented. Thus, by providingthe plurality of covering particles 222 on the anode active material221, sufficient input and output characteristics are obtained even inthe case thickening of the anode active material layer 22B and increaseof the volume density of the anode active material layer 22B areimplemented.

In particular, when the anode active material 221 contains naturalgraphite as a carbon material, the battery capacity and the cyclecharacteristics are further improved. Further, when the ratio of theplurality of covering particles 222 to the anode active material 221 isin the range from 0.1 wt % to 10 wt %, the cycle characteristics arefurther improved.

Further, if the thickness of the anode active material layer 22B is inthe range from 60 μm to 120 μm, or if the volume density of the anodeactive material layer 22B is in the range from 1.70 g/cm³ to 1.95 g/cm³,the cycle characteristics are further improved.

Second Battery

FIG. 6 shows an exploded perspective structure of a second battery. Inthe battery, a spirally wound electrode body 30 to which a cathode lead31 and an anode lead 32 are attached is contained in a film packagemember 40. The battery structure using the film package member 40 iscalled laminated film type.

The cathode lead 31 and the anode lead 32 are respectively derived inthe same direction from inside to outside of the package member 40. Thecathode lead 31 is made of, for example, a metal material such asaluminum, and the anode lead 32 is made of, for example, a metalmaterial such as copper, nickel, and stainless. The metal materialcomposing the cathode lead 31 and the anode lead 32 is in the shape of athin plate or mesh.

The package member 40 is made of a rectangular aluminum laminated filmin which, for example, a nylon film, an aluminum foil, and apolyethylene film are bonded together in this order. In the packagemember 40, for example, the polyethylene film and the spirally woundelectrode body 30 are opposed to each other, and the respective outeredges are contacted to each other by fusion bonding or an adhesive.Adhesive films 41 to protect from entering of outside air are insertedbetween the package member 40 and the cathode lead 31, the anode lead32. The adhesive film 41 is made of a material having contactcharacteristics to the cathode lead 31 and the anode lead 32, forexample, is made of a polyolefin resin such as polyethylene,polypropylene, modified polyethylene, and modified polypropylene.

The package member 40 may be made of a laminated film having otherstructure, a polymer film made of polypropylene or the like, or a metalfilm, instead of the foregoing three-layer aluminum laminated film.

FIG. 7 shows a cross sectional structure taken along line VII-VII of thespirally wound electrode body 30 shown in FIG. 6. In the spirally woundelectrode body 30, a cathode 33 and an anode 34 are layered with aseparator 35 and an electrolyte 36 in between and then spirally wound.The outermost periphery thereof is protected by a protective tape 37.

The cathode 33 has a structure in which a cathode active material layer33B is provided on the both faces of a cathode current collector 33A.The anode 34 has a structure in which an anode active material layer 34Bis provided on the both faces of an anode current collector 34A.Structures of the cathode current collector 33A, the cathode activematerial layer 33B, the anode current collector 34A, the anode activematerial layer 34B, and the separator 35 are respectively similar tothose of the cathode current collector 21A, the cathode active materiallayer 21B, the anode current collector 22A, the anode active materiallayer 22B, and the separator 23 in the first battery.

FIG. 8 and FIG. 9 show cross sectional structures of an anode material340 used for the anode active material layer 34B. FIG. 8 and FIG. 9respectively correspond to FIG. 4 and FIG. 5. The anode material 340 hasa structure similar to that of the anode material 220 in the firstbattery. Before the initial charge, as shown in FIG. 8, the anodematerial 340 has a plurality of covering particles 342 on the surface ofan anode active material 341. After the initial charge, as shown in FIG.9, the anode material 340 have a coat 343 together with the anode activematerial 341 and the plurality of covering particles 342. The structuresof the anode active material 341, the covering particles 342, and thecoat 343 are respectively similar to the structures of the anode activematerial 221, the covering particles 222, and the coat 223 in the firstbattery.

The electrolyte 36 is so-called gelatinous, containing an electrolyticsolution and a polymer compound that holds the electrolytic solution.The gel electrolyte is preferable, since a high ion conductivity (forexample, 1 mS/cm or more at room temperature) is thereby obtained, andleakage of the battery is thereby prevented.

As the polymer compound, for example, an ether polymer compound such aspolyethylene oxide and a cross-linked body containing polyethyleneoxide, an ester polymer compound such as polymethacrylate or an acrylatepolymer compound, or a polymer of vinylidene fluoride such aspolyvinylidene fluoride and a copolymer of vinylidene fluoride andhexafluoropropylene are cited. One thereof is used singly, or aplurality thereof are used by mixing. In particular, in terms of redoxstability, the fluorinated polymer compound such as the polymer ofvinylidene fluoride is preferable. The additive amount of the polymercompound in the electrolytic solution varies according to compatibilitytherebetween, but is preferably in the range from 5 wt % to 50 wt %.

The composition of the electrolytic solution is similar to thecomposition of the electrolytic solution in the foregoing first battery.However, the solvent in the second battery means a wide conceptincluding not only the liquid solvent but also a solvent having ionconductivity capable of dissociating the electrolyte salt. Therefore,when the polymer compound having ion conductivity is used, the polymercompound is also included in the solvent.

Instead of the electrolyte 36 in which the electrolytic solution is heldby the polymer compound, the electrolytic solution may be directly used.In this case, the electrolytic solution is impregnated in the separator35.

In the secondary battery, when charged, for example, lithium ions aredeintercalated from the cathode 33 and intercalated in the anode 34through the electrolyte 36. Meanwhile, when discharged, lithium ions aredeintercalated from the anode 34 and intercalated in the cathode 33through the electrolyte 36.

The secondary battery may be manufactured, for example, by the followingthree manufacturing methods.

In the first manufacturing method, first, the cathode 33 is formed byforming the cathode active material layer 33B on the both faces of thecathode current collector 33A, and the anode 34 is formed by forming theanode active material layer 34B on the both faces of the anode currentcollector 34A by a procedure similar to that of the method ofmanufacturing the first battery. Subsequently, a precursor solutioncontaining an electrolytic solution, a polymer compound, and a solventis prepared. After the cathode 33 and the anode 34 are coated with theprecursor solution, the solvent is volatilized to form the gelelectrolyte 36. Subsequently, the cathode lead 31 and the anode lead 32are respectively attached to the cathode current collector 33A and theanode current collector 34A. Subsequently, the cathode 33 and the anode34 formed with the electrolyte 36 are layered with the separator 35 inbetween to obtain a laminated body. After that, the laminated body isspirally wound in the longitudinal direction, the protective tape 37 isadhered to the outermost periphery thereof to form the spirally woundelectrode body 30. Finally, for example, after the spirally woundelectrode body 30 is sandwiched between two pieces of the film packagemembers 40, outer edges of the package members 40 are contacted bythermal fusion bonding or the like to enclose the spirally woundelectrode body 30. Then, the adhesive films 41 are inserted between thecathode lead 31, the anode lead 32 and the package member 40. Thereby,the secondary battery is fabricated.

In the second manufacturing method, first, the cathode lead 31 and theanode lead 32 are respectively attached to the cathode 33 and the anode34. After that, the cathode 33 and the anode 34 are layered with theseparator 35 in between and spirally wound. The protective tape 37 isadhered to the outermost periphery thereof, and thereby a spirally woundbody as a precursor of the spirally wound electrode body 30 is formed.Subsequently, after the spirally wound body is sandwiched between twopieces of the film package members 40, the outermost peripheries exceptfor one side are thermally fusion-bonded to obtain a pouched state, andthe spirally wound body is contained in the pouch-like package member40. Subsequently, a composition of matter for electrolyte containing anelectrolytic solution, a monomer as a raw material for the polymercompound, a polymerization initiator, and if necessary other materialsuch as a polymerization inhibitor is prepared, which is injected intothe pouch-like package member 40. After that, the opening of the packagemember 40 is hermetically sealed by thermal fusion bonding or the like.Finally, the monomer is thermally polymerized to obtain a polymercompound. Thereby, the gel electrolyte 36 is formed. Accordingly, thesecondary battery is fabricated.

In the third manufacturing method, first, the spirally wound body isformed and contained in the pouch-like package member 40 in the samemanner as that of the foregoing first manufacturing method, except thatthe separator 35 with the both faces coated with a polymer compound isused. As the polymer compound with which the separator 35 is coated, forexample, a polymer containing vinylidene fluoride as a component, thatis, a homopolymer, a copolymer, a multicomponent copolymer and the likeare cited. Specifically, polyvinylidene fluoride, a binary copolymercontaining vinylidene fluoride and hexafluoropropylene as a component, aternary copolymer containing vinylidene fluoride, hexafluoropropylene,and chlorotrifluoroethylene as a component and the like are cited. As apolymer compound, in addition to the foregoing polymer containingvinylidene fluoride as a component, another one or more polymercompounds may be used. Subsequently, an electrolytic solution isprepared and injected into the package member 40. After that, theopening of the package member 40 is sealed by thermal fusion bonding orthe like. Finally, the resultant is heated while a weight is applied tothe package member 40, and the separator 35 is contacted to the cathode33 and the anode 34 with the polymer compound in between. Thereby, theelectrolytic solution is impregnated into the polymer compound, and thepolymer compound is gelated to form the electrolyte 36. Accordingly, thesecondary battery is fabricated.

In the third manufacturing method, the swollenness characteristics areimproved compared to the first manufacturing method. Further, in thethird manufacturing method, the monomer as a raw material of the polymercompound, the solvent and the like hardly remain in the electrolyte 36compared to in the second manufacturing method, and the steps of formingthe polymer compound are favorably controlled. Thus, sufficient contactcharacteristics are obtained between the cathode 33/the anode 34/theseparator 35 and the electrolyte 36.

The action and the effect of the laminated film type secondary batteryand the method of manufacturing it are similar to those of the foregoingfirst battery.

Second Embodiment

A description will be hereinafter given of a second embodiment.

The anode material of this embodiment has a structure similar to that ofthe anode material of the first embodiment (refer to FIG. 1), exceptthat the component material of the anode active material 1 is different.

The anode active material 1 contains, for example, a material containingat least one of a metal element and a metalloid element as one or morematerials capable of intercalating and deintercalating the electrodereactant, since a high energy density is thereby obtained. Such amaterial containing at least one of a metal element and a metalloidelement may be a simple substance, an alloy, or a compound of a metalelement or a metalloid element, or may have one or more phases thereofat least in part.

The alloy in the present application includes an alloy containing one ormore metal elements and one or more metalloid elements, in addition toan alloy composed of two or more metal elements. Further, the alloy maycontain a nonmetallic element. The texture thereof includes a solidsolution, a eutectic crystal (eutectic mixture), an intermetalliccompound, and a texture in which two or more thereof coexist.

As the foregoing metal element or the foregoing metalloid element, forexample, a metal element or a metalloid element capable of forming analloy with the electrode reactant is cited. Specifically, magnesium,boron, aluminum, gallium, indium, silicon, germanium, tin, lead (Pb),bismuth, cadmium (Cd), silver, zinc, hafnium, zirconium, yttrium (Y),palladium (Pd), platinum (Pt) and the like are cited. Specially, atleast one selected from the group consisting of silicon and tin ispreferable. Silicon and tin have the high ability to intercalate anddeintercalate the electrode reactant, and thus provide an extremely highenergy density.

As a material containing at least one of silicon and tin, for example,the simple substance, an alloy, or a compound of silicon; the simplesubstance, an alloy, or a compound of tin; or a material having one ormore phases thereof at least in part is cited. Each thereof may be usedsingly, or a plurality thereof may be used by mixture.

As the alloy of silicon, for example, a material containing at least oneselected from the group consisting of tin, nickel, copper, iron, cobalt,manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony,and chromium as the second element other than silicon is cited. As thecompound of silicon, for example, a material containing oxygen or carbonis cited, and may contain the foregoing second element in addition tosilicon. Examples of an alloy or a compound of silicon include, forexample, SiB₄, SiB₆, Mg₂Si, Ni₂Si, TiSi₂, MoSi₂, CoSi₂, NiSi₂, CaSi₂,CrSi₂, Cu₅Si, FeSi₂, MnSi₂, NbSi₂, TaSi₂, VSi₂, WSi₂, ZnSi₂, SiC, Si₃N₄,Si₂N₂O, SiO_(v) (0<v≦2), SnO_(w) (0<w≦2), LiSiO or the like is cited.

As the alloy of tin, for example, a material containing at least oneselected from the group consisting of silicon, nickel, copper, iron,cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth,antimony, and chromium as the second element other than tin is cited. Asthe compound of tin, for example, a compound containing oxygen or carbonis cited. The compound may contain the foregoing second element inaddition to tin. Examples of the alloy or the compound of tin includeSnSiO₃, LiSnO, Mg₂Sn or the like.

In particular, as the material containing at least one of silicon andtin, for example, a material containing the second element and the thirdelement in addition to tin as the first element is preferable. As thesecond element, for example, at least one selected from the groupconsisting of cobalt, iron, magnesium, titanium, vanadium, chromium,manganese, nickel, copper, zinc, gallium, zirconium, niobium,molybdenum, silver, indium, cerium, hafnium, tantalum, tungsten,bismuth, and silicon is cited. As the third element, for example, atleast one selected from the group consisting of boron, carbon, aluminum,and phosphorus is cited. When the second element and the third elementare contained in addition to tin, the cycle characteristics areimproved.

Specially, a SnCoC-containing material that contains tin, cobalt, andcarbon as an element in which the carbon content is in the range from9.9 wt % to 29.7 wt %, and the cobalt ratio to the total of tin andcobalt (Co/(Sn+Co)) is in the range from 30 wt % to 70 wt % ispreferable. In such a composition range, a high energy density isobtained.

The SnCoC-containing material may further contain other elementaccording to needs. As other element, for example, silicon, iron,nickel, chromium, indium, niobium, germanium, titanium, molybdenum,aluminum, phosphorus, gallium, bismuth or the like is preferable. Two ormore thereof may be contained, since thereby higher effects areobtained.

The SnCoC-containing material has a phase containing tin, cobalt, andcarbon. Such a phase preferably has a low crystallinity structure or anamorphous structure. Further, in the SnCoC-containing material, at leastpart of carbon as an element is preferably bonded to a metal element ora metalloid element as other element. Cohesion or crystallization of tinor the like may be thereby inhibited.

The SnCoC-containing material may be formed by, for example, mixing rawmaterials of each element, dissolving the resultant mixture in anelectric furnace, a high frequency induction furnace, an arc meltingfurnace or the like and then solidifying the resultant. Otherwise, theSnCoC-containing material may be formed by various atomization methodssuch as gas atomizing and water atomizing; various roll methods; or amethod using mechanochemical reaction such as mechanical alloying methodand mechanical milling method. Specially, the SnCoC-containing materialis preferably formed by the method using mechanochemical reaction, sincethereby the anode active material 1 may have a low crystalline structureor an amorphous structure. For the method using the mechanochemicalreaction, for example, a manufacturing apparatus such as a planetaryball mill apparatus and an attliter may be used.

As a measurement method for examining bonding state of elements, forexample, X-ray Photoelectron Spectroscopy (XPS) is cited. In XPS, in thecase of graphite, the peak of 1 s orbit of carbon (Cis) is observed at a284.5 eV in the apparatus in which energy calibration is made so thatthe peak of 4f orbit of gold atom (Au4f) is obtained in 84.0 eV. In thecase of surface contamination carbon, the peak is observed at 284.8 eV.Meanwhile, in the case of higher electric charge density of carbonelement, for example, when carbon is bonded to a metal element or ametalloid element, the peak of C1s is observed in the region lower than284.5 eV. That is, when the peak of the composite wave of C1s obtainedfor the SnCoC-containing material is observed in the region lower than284.5 eV, at least part of carbon contained in the SnCoC-containingmaterial is bonded to the metal element or the metalloid element asother element.

In XPS, for example, the peak of C1s is used for correcting the energyaxis of spectrums. Since surface contamination carbon generally existson the surface, the peak of C1s of the surface contamination carbon isset to in 284.8 eV, which is used as an energy reference. In XPS, thewaveform of the peak of C1s is obtained as a form including the peak ofthe surface contamination carbon and the peak of carbon in theSnCoC-containing material. Therefore, for example, by performinganalysis by using commercially available software, the peak of thesurface contamination carbon and the peak of carbon in theSnCoC-containing material are separated. In the analysis of thewaveform, the position of the main peak existing on the lowest boundenergy side is set to the energy reference (284.8 eV).

The anode material may be manufactured by a procedure similar to that ofthe first embodiment. At this time, the anode active material 1 may beformed by, for example, coating method, vapor-phase deposition method,liquid-phase deposition method, spraying method, firing method, or acombination of two or more of these methods. As vapor-phase depositionmethod, for example, physical deposition method or chemical depositionmethod is cited. Specifically, vacuum evaporation method, sputteringmethod, ion plating method, laser ablation method, thermal ChemicalVapor Deposition (CVD) method, plasma CVD method and the like are cited.As liquid-phase deposition method, a known technique such aselectrolytic plating and electroless plating may be used. Firing methodis, for example, a method in which a particulate anode active materialmixed with a binder or the like is dispersed in a solvent and the anodecurrent collector is coated with the resultant, and then heat treatmentis provided at a temperature higher than the melting point of the binderor the like. For firing method, a known technique such as atmospherefiring method, reactive firing method, and hot press firing method isavailable as well.

According to the anode material and the method of manufacturing it ofthis embodiment, the anode active material 1 is formed from the materialcontaining at least one of the metal element and the metalloid elementas a material capable of intercalating and deintercalating the electrodereactant, and the plurality of covering particles 2 containing at leastone of the alkali metal salt and the alkali earth metal salt are formedon the surface of the anode active material 1. Thus, by an actionsimilar to that of the first embodiment, the anode material and themethod of manufacturing it of this embodiment contribute to improve theperformance of the electrochemical device using the anode material.

In particular, when the anode active material 1 contains at least oneselected from the group consisting of the simple substance, an alloy,and a compound of silicon; and the simple substance, an alloy and acompound of tin, or when the anode active material 1 contains thematerial containing tin as the first element, cobalt or the like as thesecond element, and boron or the like as the third element, highereffects are obtained.

Other effects of the anode material and the method of manufacturing itof this embodiment are similar to those of the first embodiment.

The anode material and the method of manufacturing it of this embodimentmay be used for the first and the second batteries as the firstembodiment.

In the first battery, in the case where the simple substance, an alloy,or a compound of silicon; the simple substance, an alloy, or a compoundof tin; or a material having one or more phases thereof at least in partis used as a component material of the anode active material 221, forexample, it is preferable that the anode active material 221 is formedby vapor-phase deposition method, liquid-phase deposition method,spraying method, firing method, or a combination of two or more of thesemethods, and the anode active material layer 22B and the anode currentcollector 22A are alloyed in at least part of the interface thereof.Specifically, it is preferable that at the interface thereof, theelement of the anode current collector 22A is diffused in the anodeactive material layer 22B; or the element of the anode active materiallayer 22B is diffused in the anode current collector 22A; or the bothelements are diffused in each other. Thereby, destruction due toexpansion and shrinkage of the anode active material layer 22Bassociated with charge and discharge is inhibited, and the electronconductivity between the anode active material layer 22B and the anodecurrent collector 22A is improved. The same is applied to the secondbattery.

In a secondary battery and a method of manufacturing it using the anodematerial and the method of manufacturing it, effects similar to those ofthe first and the second batteries described above are also obtained. Inparticular, since the anode active materials 221 and 341 contain thematerial containing at least one of the metal element and the metalloidelement, a high battery capacity is obtained.

EXAMPLES

Specific examples of the present application will be described indetail.

Example 1-1

The cylindrical type secondary battery shown in FIG. 2 to FIG. 4 wasmanufactured by the following procedure. The secondary battery wasmanufactured as a lithium ion secondary battery in which the capacity ofthe anode 22 was expressed based on intercalation and deintercalation oflithium.

First, the cathode 21 was formed. First, lithium carbonate (Li₂CO₃) andcobalt carbonate (CoCO₃) were mixed at a molar ratio of 0.5:1. Afterthat, the mixture was fired in the air at 900 deg C for 5 hours.Thereby, lithium cobalt complex oxide (LiCoO₂) was obtained. When thelithium cobalt complex oxide was analyzed by X-ray diffraction method,the obtained peak well corresponded with the peak registered in JointCommittee of Powder Diffraction Standard (JCPDS) file. Subsequently, thelithium cobalt complex oxide was pulverized into powder. After that, 95parts by weight of the lithium cobalt complex oxide powder and 5 partsby weight of lithium carbonate powder were mixed to obtain a cathodeactive material. Thhe cumulative 50% particle diameter of the lithiumcobalt complex oxide measured by laser diffraction was 15 μm.Subsequently, 94 parts by weight of the cathode active material, 3 partsby weight of Ketjen black as an electrical conductor (Lion Corporationmake), and 3 parts by weight of polyvinylidene fluoride as a binder weremixed to obtain a cathode mixture. After that, the cathode mixture wasdispersed in N-methyl-2-pyrrolidone as a solvent to obtain paste cathodemixture slurry. Finally, the both faces of the cathode current collector21A made of a strip-shaped aluminum foil (thickness: 20 μm) wereuniformly coated with the cathode mixture slurry, which was dried. Afterthat, the resultant was compression-molded by a roll pressing machine toform the cathode active material layer 21B. The thickness of the cathodeactive material layer 21B on a single face side of the cathode currentcollector 21A was 97 μm, and the volume density was 3.55 g/cm³.

Next, the anode 22 was formed. First, as the anode active material 221,particulate graphite powder (Mesocarbon Microbead (MCMB)) as a carbonmaterial was prepared. The lattice spacing d₀₀₂ in the C-axis directionmeasured by X-ray diffraction method was 0.3363 nm, the average particlediameter was 25 μm, and the specific surface area measured by nitrogen(N₂) Brunauer-Emmett-Teller (BET) method was 0.8 m²/g. Subsequently,lithium chloride (LiCl) powder as an alkali metal salt was dissolved inwater to prepare a lithium chloride water solution. After MCMB wasdipped in the lithium chloride water solution, the resultant wasagitated for 1 hour. Subsequently, the lithium chloride water solutionin which MCMB was dipped was filtered. After that, the resultant wasvacuum-dried for 1 hour at 120 deg C, lithium chloride was precipitatedon the surface of the anode active material 221 to form the plurality ofcovering particles 222. Thereby, the anode material 220 was obtained.

When the specific surface area of the obtained anode material 220 wasmeasured by nitrogen gas BET method, the specific surface area of theanode active material 221 was decreased by about 5%. Further, visualinspection was performed for the color appearance of the anode materialbefore and after the covering particles 222 were formed, the color waschanged from black to gray over the entire area. Based on the decreasedspecific surface area and the change of color appearance, it wasconfirmed that the covering particles 222 were formed on the surface ofthe anode active material 221. For reference, the surface of the anodematerial 220 was observed by a Scanning Electron Microscope (SEM) at tenthousand times magnification. In the result, the covering particles 222were not observed on the surface of the anode active material 221 atsuch a magnification. Accordingly, it was found that the particlediameter of each covering particle 222 was submicron scale or less.

When the covering particles 222 were formed, the water weight wasmaintained constant, the amount of lithium chloride dissolved thereinwas adjusted, and thereby the ratio of the plurality of coveringparticles 222 to the anode active material 221 was 1 wt %. Forconfirmation, the weight difference between before and after forming thecovering particles 222 was examined. In the result, the weightdifference corresponded with the dissolution amount of lithium chloride.Accordingly, it was confirmed that all lithium chloride in the lithiumchloride water solution was precipitated on the surface of the anodeactive material 221.

Subsequently, 90 parts by weight of the anode material 220 and 10 partsby weight of polyvinylidene fluoride as a binder were mixed to obtain ananode mixture. After that, the anode mixture was dispersed inN-methyl-2-pyrrolidone as a solvent to obtain paste anode mixtureslurry. Finally, the both faces of the anode current collector 22A madeof a strip-shaped electrolytic copper foil (thickness: 15 μm) wereuniformly coated with the anode mixture slurry, which was dried. Afterthat, the resultant was compression-molded by a roll pressing machine toform the anode active material layer 22B. The thickness of the anodeactive material layer 22B on a single face side of the anode currentcollector 22A was 90 μm, and the volume density was 1.81 g/cm³.

Subsequently, the secondary battery was assembled by using the cathode21 and the anode 22. First, the cathode lead 25 made of aluminum wasattached to one end of the cathode current collector 21A by welding, andthe anode lead 26 made of nickel was attached to one end of the anodecurrent collector 22A by welding. Subsequently, the cathode 21, theseparator 23 (thickness: 25 μm) made of a microporous polyethylenestretched film, the anode 22, and the foregoing separator 23 werelayered in this order. The resultant laminated body was spirally woundto form the spirally wound electrode body 20. Subsequently, the cathodelead 25 was welded to the safety valve mechanism 15, and the anode lead26 was welded to the battery can 11. After that, while the spirallywound electrode body 20 was sandwiched between the pair of insulatingplates 12 and 13, the spirally wound electrode body 20 was contained inthe battery can 11 made of nickel-plated iron. Subsequently, anelectrolytic solution was prepared. After that, the electrolyticsolution was injected into the battery can 11 by depressurizationmethod, and impregnated in the separator 23. When the electrolyticsolution was prepared, ethylene carbonate, diethyl carbonate, propylenecarbonate, and vinylethylene carbonate as a solvent were mixed at aweight ratio of 50:30:17:3 to obtain a mixture. After that, lithiumhexafluorophosphate (LiPF₆) as an electrolyte salt was dissolved in themixture so that the concentration in the electrolytic solution was 1mol/kg. Finally, the safety valve mechanism 15, the PTC device 16, andthe battery cover 14 were fixed by caulking the battery can 11 with thegasket 17 coated with asphalt. Thereby, the air tightness of inside ofthe battery can 11 was secured, and the cylindrical type secondarybattery being 18 mm in diameter and 65 mm high was fabricated.

Examples 1-2 to 1-6

A procedure was performed in the same manner as that of Example 1-1,except that sodium chloride (NaCl: Example 1-2), potassium chloride(KCl: Example 1-3), lithium carbonate (Li₂CO₃: Example 1-4), sodiumcarbonate (Na₂CO₃: Example 1-5), or potassium carbonate (K₂CO₃: Example1-6) was used as an alkali metal salt.

Examples 1-7 and 1-8

A procedure was performed in the same manner as that of Example 1-1,except that magnesium carbonate (MgCO₃: Example 1-7) or calciumcarbonate (CaCO₃: Example 1-8) was used as an alkali earth metal saltinstead of the alkali metal salt.

Comparative Example 1

A procedure was performed in the same manner as that of Examples 1-1 to1-8, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 1-1 to 1-8 and Comparativeexample 1 were examined, the results shown in Table 1 were obtained.

In examining the input and output characteristics, after the secondarybattery was charged and discharged in the atmosphere at 23 deg C, theinitial charge and discharge efficiency (%)=(discharge capacity/chargecapacity)×100 was calculated. At that time, charge was performed at theconstant current of 1 C until the battery voltage reached 4.2 V, chargewas continuously performed at the constant voltage of 4.2 V until thetotal charge time reached 4 hours. After that, discharge was performedat the constant current of 1500 mA until the battery voltage reached 3.0V. The foregoing “1 C” means a current value with which the theoreticalcapacity is completely discharged in 1 hour.

In examining the cycle characteristics, charge and discharge wereperformed 1 cycle in the atmosphere at 23 deg C to measure the dischargecapacity, and then charge and discharge were continuously performed inthe same atmosphere until the total number of cycles was 100 cycles tomeasure the discharge capacity. After that, the discharge capacityretention ratio (%)=(discharge capacity at the 100th cycle/dischargecapacity at the first cycle)×100 was calculated. The charge anddischarge conditions were similar to those in the case of examining theinput and output characteristics.

The procedure and the conditions for examining the foregoing input andoutput characteristics and the foregoing cycle characteristics weresimilarly applied to the following examples and comparative examples.

TABLE 1 Anode active material layer Initial Discharge Anode materialcharge and capacity Anode Covering particles Volume discharge retentionCylindrical active Ratio Thickness density efficiency ratio typematerial Type (wt %) (μm) (g/cm³) (%) (%) Example 1-1 MCMB LiCl 1 901.81 91.5 83 Example 1-2 NaCl 91.1 85 Example 1-3 KCl 91 85 Example 1-4Li₂CO₃ 91.6 92 Example 1-5 Na₂CO₃ 91 88 Example 1-6 K₂CO₃ 91.6 92Example 1-7 MgCO₃ 91.1 79 Example 1-8 CaCO₃ 91.2 80 Comparative MCMB — —90 1.81 90.2 64 example 1

As shown in Table 1, in Examples 1-1 to 1-8 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative example 1 in which the plurality ofcovering particles 222 were not formed irrespective of the type ofalkali metal salt and alkali earth metal salt. Table 1 discloses noexample in which an alkali metal salt and an alkali earth metal salt aremixed. However, it is evident from the results of Table 1 that theforegoing result was obtained when the alkali metal salt or the alkaliearth metal salt was independently used. In addition, there is noparticular reason for a lowered initial charge and discharge efficiencyand a lowered discharge capacity retention ratio in the case of mixingthe alkali metal salt and the alkali earth metal salt. Thus, it isevident that similar effects are also obtained when both the alkalimetal salt and the alkali earth metal salt are mixed.

Accordingly, in the secondary battery of an embodiment, it was confirmedthat the input and output characteristics were secured and the cyclecharacteristics were improved when the plurality of covering particlescontaining at least one of the alkali metal salt and the alkali earthmetal salt were formed on the surface of the anode active material inthe case that MCMB was used as an anode active material.

Examples 2-1 to 2-5

A procedure was performed in the same manner as that of Example 1-6,except that the thickness of the anode active material layer 22B was 95μm, and the ratio of the plurality of covering particles 222 to theanode active material 221 was 0.05 wt % (Example 2-1), 0.1 wt % (Example2-2), 1 wt % (Example 2-3), 10 wt % (Example 2-4), or 15 wt % (Example2-5). In this case, the dissolution amount of potassium carbonate andthe mixture ratio between the potassium carbonate water solution and theanode active material 221 were adjusted so that the ratio was theforegoing each value.

Comparative Example 2

A procedure was performed in the same manner as that of Examples 2-1 to2-5, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 2-1 to 2-5 and Comparativeexample 2 were examined, the results shown in Table 2 and FIG. 10 wereobtained.

TABLE 2 Anode active material layer Initial Discharge Anode materialcharge and capacity Anode Covering particles Volume discharge retentionCylindrical active Ratio Thickness density efficiency ratio typematerial Type (wt %) (μm) (g/cm³) (%) (%) Example 2-1 MCMB K₂CO₃ 0.05 951.81 90.2 61 Example 2-2 0.1 91.2 72 Example 2-3 1 91.5 90 Example 2-410 91.7 81 Example 2-5 15 90.3 56 Comparative MCMB — — 95 1.81 90.2 54example 2

As shown in Table 2, in Examples 2-1 to 2-5 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency was equal to or more than that of Comparative example 2 inwhich the plurality of covering particles 222 were not formed, and thedischarge capacity retention ratio was higher than that of Comparativeexample 2. In this case, focusing attention on the ratio of theplurality of covering particles 222 to the anode active material 221, asshown in Table 2 and FIG. 10, the initial charge and discharge retentionratio was almost constant not depending on the ratio, while thedischarge capacity retention ratio tended to be largely high if theratio was in the range from 0.1 wt % to 10 wt %.

Accordingly, in the secondary battery of an embodiment, it was confirmedthat the cycle characteristics were further improved if the ratio of theplurality of covering particles to the anode active material is in therange from 0.1 wt % to 10 wt %.

Examples 3-1 to 3-4

A procedure was performed in the same manner as that of Example 1-6,except that the thickness of the anode active material layer 22B was 50μm (Example 3-1), 60 μm (Example 3-2), 120 μm (Example 3-3), or 130 μm(Example 3-4).

Comparative examples 3-1 to 3-4

A procedure was performed in the same manner as that of Examples 3-1 to3-4, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 3-1 to 3-4 and Comparativeexamples 3-1 to 3-4 were examined, the results shown in Table 3 wereobtained. “Increase in retention ratio” shown in Table 3 means anincrease amount of the discharge capacity retention ratio whencomparison was made between Examples 1-6, 2-3, 3-1 to 3-4 andComparative examples 1, 2, and 3-1 to 3-4 for every same thickness ofthe anode active material layer 22B. The same will be applied to theafter-mentioned examples.

TABLE 3 Anode active material layer Initial Discharge Anode materialcharge and capacity Increase Anode Covering particles Volume dischargeretention in Cylindrical active Ratio Thickness density efficiency ratioretention type material Type (wt %) (μm) (g/cm³) (%) (%) ratio Example3-1 MCMB K₂CO₃ 1 50 1.81 91.5 94 +4 Example 3-2 60 91.4 94 +18 Example1-6 90 91.6 92 +28 Example 2-3 95 91.5 90 +36 Example 3-3 120 91.5 75+56 Example 3-4 130 91.3 26 +9 Comparative MCMB — — 50 1.81 90.3 90 —example 3-1 Comparative 60 90.2 76 — example 3-2 Comparative 90 90.2 64— example 1 Comparative 95 90.2 54 — example 2 Comparative 120 90.2 19 —example 3-3 Comparative 130 90 17 — example 3-4

As shown in Table 3, in Examples 3-1 to 3-4 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative examples 3-1 to 3-4 in which theplurality of covering particles 222 were not formed.

In this case, when comparison was made between the examples and thecomparative examples for every same thickness of the anode activematerial layer 22B, the increase in retention ratio tended to be largelyincreased if the thickness was in the range from 60 μm to 120 μm. Theresult showed the effect of the plurality of covering particles 222 onthe discharge capacity retention ratio as follows. If the thickness ofthe anode active material layer 22B was smaller than 60 μm, the currentdensity of the anode 22 was substantially low in charge, the transferrate of lithium ions was fast at the interface between the anode activematerial layer 22B and the electrolytic solution as the rate-determiningprocess of electrode reaction, and thus effect of forming the coveringparticles 222 was not sufficiently shown. Meanwhile, if the thickness ofthe anode active material layer 22B was larger than 120 μm, the currentdensity of the anode 22 was excessively high in charge, and thus lithiumions were not transferred sufficiently at the foregoing interface evenin the case of forming the covering particles 222. In the result, inthis case, the effect of forming the covering particles 222 was notsufficiently shown. On the other hand, if the thickness of the anodeactive material layer 22B was in the range from 60 μm to 120 μm, even inthe case that the current density of the anode 22 was high in charge,lithium ions were easily transferred due to the covering particles 222.Accordingly, in this case, the effect of forming the covering particles222 was sufficiently shown.

Accordingly, in the secondary battery of an embodiment, it was confirmedthat the input and output characteristics were also secured and thecycle characteristics were also improved in the case that the thicknessof the anode active material layer was changed. In addition, it wasconfirmed that the cycle characteristics were further improved if thethickness was in the range from 60 μm to 120 μm.

Examples 4-1 to 4-4

A procedure was performed in the same manner as that of Example 2-3,except that the volume density of the anode active material layer 22Bwas 1.60 g/cm³, (Example 4-1), 1.70 g/cm³ (Example 4-2), 1.95 g/cm³(Example 4-3), or 2.00 g/cm³ (Example 4-4).

Comparative examples 4-1 to 4-4

A procedure was performed in the same manner as that of Examples 4-1 to4-4, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 4-1 to 4-4 and Comparativeexamples 4-1 to 4-4 were examined, the results shown in Table 4 wereobtained.

TABLE 4 Anode active material layer Initial Discharge Anode materialcharge and capacity Increase Anode Covering particles Volume dischargeretention in Cylindrical active Ratio Thickness density efficiency ratioretention type material Type (wt %) (μm) (g/cm³) (%) (%) ratio Example4-1 MCMB K₂CO₃ 1 95 1.60 91.4 93 +2 Example 4-2 1.70 91.5 93 +22 Example2-3 1.81 91.5 90 +36 Example 4-3 1.95 91.5 82 +48 Example 4-4 2.00 91.127 +6 Comparative MCMB — — 95 1.60 90 91 — example 4-1 Comparative 1.7090.2 71 — example 4-2 Comparative 1.81 90.2 54 — example 2 Comparative1.95 90.1 34 — example 4-3 Comparative 2.00 90 21 — example 4-4

As shown in Table 4, in Examples 4-1 to 4-4 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative examples 4-1 to 4-4 in which theplurality of covering particles 222 were not formed.

In this case, when the respective increase in retention ratios werecompared to each other based on the respective volume densities of theanode active material layer 22B, the increase in retention ratio tendedto be largely increased if the volume density was in the range from 1.70g/cm³ to 1.95 g/cm³. The result showed the effect of the plurality ofcovering particles 222 on the discharge capacity retention ratio asfollows. If the volume density of the anode active material layer 22Bwas lower than 1.70 g/cm³, the transfer rate of lithium ions in theanode 22 in charge was fast, and the transfer rate of lithium ions wassimilarly fast at the interface between the anode active material layer22B and the electrolytic solution as the rate-determining process ofelectrode reaction, and thus effect of forming the covering particles222 was not sufficiently shown. Meanwhile, if the volume density of theanode active material layer 22B was higher than 1.95 g/cm³, the transferrate of lithium ions in the anode 22 in charge was slow, and lithiumions were not transferred sufficiently at the foregoing interface evenin the case of forming the covering particles 222. In the result, inthis case, the effect of forming the covering particles 222 was notsufficiently shown. On the other hand, when the volume density of theanode active material layer 22B was in the range from 1.70 g/cm³ to 1.95g/cm³, even if the volume density was high, lithium ions were easilytransferred due to the covering particles 222. Accordingly, in thiscase, the effect of forming the covering particles 222 was sufficientlyshown.

Accordingly, in the secondary battery of an embodiment, it was confirmedthat the input and output characteristics were also secured and thecycle characteristics were also improved when the volume density of theanode active material layer was changed. In addition, it was confirmedthat the cycle characteristics were further improved if the volumedensity was in the range from 1.70 g/cm³ to 1.95 g/cm³.

Example 5-1

A procedure was performed in the same manner as that of Example 2-3,except that the specific surface area of the anode active material 221was 1.5 m²/g (Example 5-1).

Examples 5-2 and 5-3

A procedure was performed in the same manner as that of Example 2-3,except that natural graphite was used instead of MCMB as the anodeactive material 221, and the specific surface area thereof was 2.2 m²/g(Example 5-2) or 4.1 m²/g (Example 5-3).

Comparative examples 5-1 to 5-3

A procedure was performed in the same manner as that of Examples 5-1 to5-3, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 5-1 to 5-3 and Comparativeexamples 5-1 to 5-3 were examined, the results shown in Table 5 wereobtained.

TABLE 5 Anode active material layer Anode material Initial DischargeAnode active material charge and capacity Increase Specific Coveringparticles Volume discharge retention in Cylindrical surface RatioThickness density efficiency ratio retention type Type area (m²/g) Type(wt %) (μm) (g/cm³) (%) (%) ratio Example 2-3 MCMB 0.8 K₂CO₃ 1 95 1.8191.5 90 +36 Example 5-1 1.5 91 89 +38 Example 5-2 Natural 2.2 90.2 87+55 Example 5-3 graphite 4.1 88.4 87 +58 Comparative MCMB 0.8 — — 951.81 90.2 54 — example 2 Comparative 1.5 89.6 51 — example 5-1Comparative Natural 2.2 87.8 32 — example 5-2 graphite Comparative 4.185.2 29 — example 5-3

As shown in Table 5, in Examples 5-1 to 5-3 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative examples 5-1 to 5-3 in which theplurality of covering particles 222 were not formed.

In this case, when the respective increase in retention ratios werecompared to each other based on the type of the anode active material221, the increase in retention ratio tended to be largely increased inthe case of using the natural graphite than in the case of using MCMB.The result showed the effect of the plurality of covering particles 222on the discharge capacity retention ratio as follows. In the case wherethe natural graphite having a high crystal and a narrow plane distancewas used, the transfer rate of lithium ions was fast at the interfacebetween the anode active material layer 22B and the electrolyticsolution compared to the case using MCMB. Thus, in this case, when thethickness and the volume density of the anode active material layer 22Bwere increased, the discharge capacity retention ratio tended to belargely lowered. In this case, when the covering particles 222 wereformed on the surface of the anode active material 221, the transferrate of lithium ions became fast even if the thickness and the volumedensity of the anode active material layer 22B were large. Accordingly,effect of forming the covering particles 222 was sufficiently shown.Further, when the covering particles 222 existed on the surface of theanode active material 221, decomposition of the electrolytic solutionwas inhibited even in the case of using the natural graphite having alarge specific surface area. In this case, the effect of forming theplurality of covering particles 222 was also sufficiently shown.

Accordingly, in the secondary battery of an embodiment, it was confirmedthat the input and output characteristics were also secured and thecycle characteristics were also improved when the type of carbonmaterial and the specific surface area thereof were changed in the casethat the carbon material was used as an anode active material. Inaddition, it was confirmed that the cycle characteristics were furtherimproved when the natural graphite was used.

Examples 6-1 to 6-8

A cylindrical type secondary battery was manufactured in the same manneras that of Examples 1-1 to 1-8 except for the following procedure.

To obtain a lithium cobalt complex oxide, a mixture of lithium carbonateand cobalt carbonate was fired at 890 deg C for 5 hours. Then, theresultant was pulverized until the particle diameter became 10 μm. Toform the cathode active material layer 21B, 91 parts by weight of amixture of the lithium cobalt complex oxide and lithium carbonate, 6parts by weight of graphite as an electrical conductor (KS-15manufactured by Lonza), and 3 parts by weight of polyvinylidene fluorideas a binder were mixed.

As the anode active material 221, a SnCoC-containing material as amaterial containing at least one of a metal element and a metalloidelement was used. That is, first, as raw materials, cobalt powder, tinpowder, and carbon powder were prepared. The cobalt powder and the tinpowder were alloyed to obtain cobalt-tin alloy powder, to which thecarbon powder was added. The resultant was dry-blended. Subsequently, 20g of the mixture together with about 400 g of a corundum having adiameter of 9 mm were set in a reactive vessel of a planetary ball millmanufactured by Itoh Seisakujo Co., Ltd. Subsequently, inside of thereactive vessel was substituted with argon atmosphere. After that,10-minute operation at 250 rpm and 10-minute stop were repeated untilthe total operation time became 30 hours. Finally, the reactive vesselwas cooled down to room temperature, the synthesized SnCoC-containingmaterial was taken out. After that, coarse grain was removed therefromwith the use of a 280-mesh sieve. When the composition of theSnCoC-containing material was analyzed, the tin content was 50 wt %, thecobalt content was 29.4 wt %, and the carbon content was 19.6 wt %. Thetin content and the cobalt content were measured by Inductively CoupledPlasma (ICP) optical emission spectroscopy. The carbon content wasmeasured by a carbon sulfur analyzer.

The obtained SnCoC-containing material was analyzed by X-ray diffractionmethod. In the result, the diffraction peak having the half bandwidth inthe range of the diffraction angle 20=20 to 50 degrees was observed.Further, when the SnCoC-containing material was analyzed by XPS, Peak P1was obtained as shown in FIG. 11. When Peak P1 was analyzed, Peak P2 ofthe surface contamination carbon and Peak P3 of C1s in theSnCoC-containing material on the energy side lower than that of Peak P2(region lower than 284.5 eV) were obtained. That is, it was confirmedthat carbon in the SnCoC-containing material was bonded to otherelement.

When the anode 22 was formed, 80 parts by weight of the anode activematerial 220 having the SnCoC-containing material as the anode activematerial 221, 11 parts by weight of graphite (Ronza make, KS-15) and 1part by weight of acetylene black as an electrical conductor, and 8parts by weight of polyvinylidene fluoride as a binder were mixed toobtain an anode mixture. After that, the mixture was dispersed inN-methyl-2-pyrrolidone as a solvent to obtain paste anode mixtureslurry. After that, the both faces of the anode current collector 22Amade of a strip-shaped electrolyte copper foil (thickness: 10 μm) wereuniformly coated with the anode mixture slurry, which was dried andcompression-molded by a rolling press machine to form the anode activematerial layer 22B.

When the secondary battery was assembled, the three-layer structureseparator 23 in which a porous polyethylene was sandwiched betweenporous polypropylene (UP3015 manufactured by Ube industries Ltd.,thickness: 25 μm) was used. Further, when the electrolytic solution wasprepared, as a solvent, ethylene carbonate, dimethyl carbonate, and4-fluoro-1,3-dioxolane-2-one as a solvent were mixed at a weight ratioof 20:60:20. After that, lithium hexafluorophosphate and lithiumbis(pentafluoroethanesulfonyl)imide (LiN(C₂F₅SO₂)₂) were dissolvedtherein as an electrolyte salt so that each concentration in theelectrolytic solution was 0.5 mol/kg.

Comparative Example 6

A procedure was performed in the same manner as that of Examples 6-1 to6-8, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 6-1 to 6-8 and Comparativeexample 6 were examined in the same manner as that of Examples 1-1 to1-8 and Comparative example 1, except that the discharge was performeduntil the discharge voltage reached 2.6 V, the results shown in Table 6were obtained. The foregoing change of discharge voltage was similarlyapplied to the following examples and comparative examples.

TABLE 6 Initial Anode active material layer charge Discharge (Anodematerial) and capacity Anode Covering particles discharge retentionactive Ratio efficiency ratio Cylindrical type material Type (wt %) (%)(%) Example 6-1 SnCoC LiCl 1 86 91.1 Example 6-2 NaCl 85 90.8 Example6-3 KCl 86 90.3 Example 6-4 Li₂CO₃ 87 92.2 Example 6-5 Na₂CO₃ 85 91.2Example 6-6 K₂CO₃ 85 91.4 Example 6-7 MgCO₃ 84 90.8 Example 6-8 CaCO₃ 8390.4 Comparative SnCoC — — 74 86.7 example 6

As shown in Table 6, in Examples 6-1 to 6-8 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative example 6 in which the plurality ofcovering particles 222 were not formed irrespective of the type ofalkali metal salt and alkali earth metal salt. Accordingly, in thesecondary battery of an embodiment, it was confirmed that the input andoutput characteristics were secured and the cycle characteristics wereimproved when the plurality of covering particles containing at leastone of the alkali metal salt and the alkali earth metal salt were formedon the surface of the anode active material in the case that theSnCoC-containing material was used as an anode active material.

Examples 7-1 to 7-4

A procedure was performed in the same manner as that of Examples 2-1,2-2, 2-4, and 2-5, except that the SnCoC-containing material was used asthe anode active material 221 as in Examples 6-1 to 6-8.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 7-1 to 7-4 were examined, theresults shown in Table 7 and FIG. 12 were obtained.

TABLE 7 Initial Anode active material layer charge Discharge (Anodematerial) and capacity Anode Covering particles discharge retentionactive Ratio efficiency ratio Cylindrical type material Type (wt %) (%)(%) Example 7-1 SnCoC K₂CO₃ 0.05 76 89.3 Example 7-2 0.1 80 90.9 Example6-6 1 85 91.4 Example 7-3 10 89 92 Example 7-4 15 89 88.6 ComparativeSnCoC — — 74 86.7 example 6

As shown in Table 7, in Examples 7-1 to 7-4 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative example 6 in which the plurality ofcovering particles 222 were not formed.

In this case, as shown in Table 7 and FIG. 12, there was a tendency thatthe initial charge and discharge efficiency was largely high if theratio was 0.1 wt % or more, and the discharge capacity retention ratiowas largely high if the ratio was 10 wt % or less. The result shows thefollowing fact. That is, if the ratio was 0.1 wt % or less, the numberof covering particles 222 was excessively small, and thus lithium ionswere not transferred at the interface between the anode active materiallayer 22B and the electrolytic solution. Meanwhile, if the ratio waslarger than 10 wt %, the number of covering particles 222 wasexcessively large, and thus the discharge capacity was easily lowered.

Accordingly, in the secondary battery of an embodiment, it was confirmedthat the initial charge and discharge efficiency and the cyclecharacteristics were further improved if the ratio of the plurality ofthe covering particles to the anode active material was in the rangefrom 0.1 wt % to 10 wt %.

Examples 8-1 to 8-6

A procedure was performed in the same manner as that of Example 6-6,except that SnMnC-containing material (Example 8-1), SnFeC-containingmaterial (Example 8-2), SnNiC-containing material (Example 8-3),SnCuC-containing material (Example 8-4), SnCoB-containing material(Example 8-5), or SnCoP-containing material (Example 8-6) was used asthe anode active material 221.

Comparative examples 8-1 to 8-6

A procedure was performed in the same manner as that of Examples 8-1 to8-6, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 8-1 to 8-6 and Comparativeexamples 8-1 to 8-6 were examined, the results shown in Table 8 wereobtained.

TABLE 8 Initial Anode active material layer charge Discharge (Anodematerial) and capacity Anode Covering particles discharge retentionactive Ratio efficiency ratio Cylindrical type material Type (wt %) (%)(%) Example 8-1 SnMnC K₂CO₃ 1 86 91.7 Example 8-2 SnFeC 84 92.3 Example8-3 SnNiC 84 92.1 Example 8-4 SnCuC 81 91.7 Example 6-6 SnCoC 85 91.4Example 8-5 SnCoB 83 90.8 Example 8-6 SnCoP 82 90.8 Comparative SnMnC —— 77 87.3 example 8-1 Comparative SnFeC 76 84.6 example 8-2 ComparativeSnNiC 78 87.7 example 8-3 Comparative SnCuC 76 86.9 example 8-4Comparative SnCoC 74 86.7 example 6 Comparative SnCoB 76 84.2 example8-5 Comparative SnCoP 71 84.9 example 8-6

As shown in Table 8, in Examples 8-1 to 8-6 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative examples 8-1 to 8-6 in which theplurality of covering particles 222 were not formed. Accordingly, in thesecondary battery of an embodiment, it was confirmed that the input andoutput characteristics were secured and the cycle characteristics wereimproved even if the metal element was changed in the case that thealloy containing tin and other metal element was used as an anode activematerial.

Examples 9-1 and 9-2

A procedure was performed in the same manner as that of Example 6-6,except that the composition (weight ratio) of the SnCoC-containingmaterial as the anode active material 221 was 56:33:9.9 (Example 9-1) or43.7:25.6:29.7 (Example 9-2).

Comparative examples 9-1 and 9-2

A procedure was performed in the same manner as that of Examples 9-1 and9-2, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 9-1 and 9-2 and Comparativeexamples 9-1 and 9-2 were examined, the results shown in Table 9 wereobtained.

TABLE 9 Initial Discharge Anode active material layer (Anode material)charge and capacity Anode active material Covering particles dischargeretention Cylindrical Weight ratio Ratio efficiency ratio type Type(Sn:Co:C) Type (wt %) (%) (%) Example 9-1 SnCoC 56:33:9.9 K₂CO₃ 1 8394.3 Example 6-6 50:29.4:19.6 85 91.4 Example 9-2 43.7:25.6:29.7 89 92Comparative SnCoC 56:33:9.9 — — 71 88.6 example 9-1 Comparative50:29.4:19.6 74 86.7 example 6 Comparative 43.7:25.6:29.7 75 82.1example 9-2

As shown in Table 9, in Examples 9-1 and 9-2 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative examples 9-1 and 9-2 in which theplurality of covering particles 222 were not formed. Accordingly, in thesecondary battery of an embodiment, it was confirmed that the input andoutput characteristics were also secured and the cycle characteristicswere also improved even when the composition of the alloy containing tinwas changed in the case that the alloy containing tin was used as ananode active material.

Examples 10-1 to 10-8

A procedure was performed in the same manner as that of Examples 6-1 to6-8, except that silicon was used as the anode active material 221instead of the SnCoC-containing material. When the anode active material221 was formed, silicon was deposited on the both faces of the anodecurrent collector 21A by electron beam evaporation method with the useof a deflective electron beam evaporation source.

Comparative Example 10

A procedure was performed in the same manner as that of Examples 10-1 to10-8, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 10-1 to 10-8 and Comparativeexample 10 were examined, the results shown in Table 10 were obtained.

TABLE 10 Initial Discharge Anode active material layer (Anode material)charge and capacity Anode active material Covering particles dischargeretention Cylindrical Forming Ratio efficiency ratio type Type methodType (wt %) (%) (%) Example 10-1 Si Electron LiCl 1 85 90.1 Example 10-2beam NaCl 85 89.9 Example 10-3 evaporation KCl 85 89.8 Example 10-4method Li₂CO₃ 90 91.2 Example 10-5 Na₂CO₃ 86 89.9 Example 10-6 K₂CO₃ 8790 Example 10-7 MgCO₃ 85 90.3 Example 10-8 Ca CO₃ 85 90.1 Comparative SiElectron — — 77 81.1 example 10 beam evaporation method

As shown in Table 10, in Examples 10-1 to 10-8 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative example 10 in which the plurality ofcovering particles 222 were not formed irrespective of the type ofalkali metal salt and alkali earth metal salt. Accordingly, in thesecondary battery of an embodiment, it was confirmed that the input andoutput characteristics were also secured and the cycle characteristicswere also improved in the case that silicon was used as an anode activematerial.

Examples 11-1 and 11-2

A procedure was performed in the same manner as that of Example 10-6,except that the anode active material 221 was formed by sputteringmethod (Example 11-1) or sintering method (Example 11-2) instead ofelectron beam evaporation method. When the anode active material 221 wasformed by sintering method, 90 parts by weight of silicon powder as theanode active material 221 (average particle diameter: 1 μm) and 10 partsby weight of polyvinylidene fluoride as a binder were mixed to obtain ananode mixture. Then, the anode mixture was dispersed inN-methyl-2-pyrrolidone as a solvent to obtain paste anode mixtureslurry. After that, the both faces of the anode current collector 22Awere uniformly coated with the anode mixture slurry, and then theresultant was fired.

Example 11-3

A procedure was performed in the same manner as that of Example 10-6,except that tin was used as the anode active material 221 instead ofsilicon and the anode active material 221 was formed by plating methodinstead of electron beam evaporation method. When the anode activematerial 221 was formed, tin was deposited on the both faces of theanode current collector 21A by electrolytic plating method with the useof a tin plating solution.

Comparative examples 11-1 to 11-3

A procedure was performed in the same manner as that of Examples 11-1 to11-3, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 11-1 to 11-3 and Comparativeexamples 11-1 to 11-3 were examined, the results shown in Table 11 wereobtained.

TABLE 11 Initial Discharge Anode active material layer (Anode material)charge and capacity Anode active material Covering particles dischargeretention Cylindrical Forming Ratio efficiency ratio type Type methodType (wt %) (%) (%) Example 10-6 Si Electron K₂CO₃ 1 87 90 beamevaporation method Example 11-1 Sputtering 88 89.6 method Example 11-2Sintering 82 90.2 method Example 11-3 Sn Plating 80 88.8 methodComparative Si Electron — — 77 81.1 example 10 beam evaporation methodComparative Sputtering 78 80.2 example 11-1 method Comparative Sintering71 83.1 example 11-2 method Comparative Sn Plating 68 83.6 example 11-3method

As shown in Table 11, in Examples 11-1 to 11-3 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative examples 11-1 to 11-3 in which theplurality of covering particles 222 were not formed. Accordingly, in thesecondary battery of an embodiment, it was confirmed that the input andoutput characteristics were also secured and the cycle characteristicswere also improved when tin was used as an anode active material or whenthe forming method was changed in the case that silicon or tin was usedas an anode active material.

Example 12-1

A procedure was performed in the same manner as that of Example 6-6,except that the laminated film type secondary battery shown in FIG. 6 toFIG. 8 was manufactured by the following procedure.

When the secondary battery was manufactured, first, the cathode 33 wasformed by forming the cathode active material layer 33B on the bothfaces of the cathode current collector 33A, and the anode 34 is formedby forming the anode active material layer 34B on the both faces of theanode current collector 34A. As an electrical conductor of the anodeactive material layer 34B, graphite (mesophase spherule/spherocrystalgraphite manufactured by JFE Steel Corporation) was used. Subsequently,copolymer of vinylidene fluoride and hexafluoropropylene was prepared asa polymer compound. After that, a precursor solution was prepared bymixing the polymer compound, an electrolytic solution, and a mixedsolvent. As the composition of the polymer compound, a component havinga weight-average molecular weight of 0.7 million and a component havinga weight-average molecular weight of 0.31 million were mixed at a weightratio of 9:1, and the ratio of hexafluoropropylene in the copolymer was7 wt %. Subsequently, the both faces of the cathode 33 and the anode 34were coated with the precursor solution by using a bar coater, the mixedsolvent was volatilized to form the gel electrolyte layer 36.Subsequently, the cathode lead 31 made of aluminum was attached to oneend of the cathode current collector 33A by welding, and the anode lead32 made of nickel was attached to one end of the anode current collector34A by welding. Subsequently, the cathode 33, the separator 35 made ofpolyethylene (E16MMS manufactured by Tonen Chemical Corporation,thickness: 16 μm), the anode 34, and the foregoing separator 35 werelayered in this order, and the resultant laminated body was spirallywound in the longitudinal direction. The end of the spirally wound bodywas fixed with the use of the protective tape 37 made of an adhesivetape to form the spirally wound electrode body 30. Finally, the spirallywound electrode body 30 was enclosed into the package member 40 made ofa three-layer laminated film (total thickness: 100 μm) in which nylon(thickness: 30 μm), aluminum (thickness: 40 μm), and cast polypropylene(thickness: 30 μm) were layered from the outside under reduced pressure.Accordingly, the laminated film type secondary battery was fabricated.

Examples 12-2 and 12-3

A procedure was performed in the same manner as that of Examples 10-6and 11-1, except that the laminated film type secondary battery wasmanufactured as in Example 12-1.

Comparative examples 12-1 to 12-3

A procedure was performed in the same manner as that of Examples 12-1 to12-3, except that the plurality of covering particles 222 were notformed.

When the input and output characteristics and the cycle characteristicsof the secondary batteries of Examples 12-1 to 12-3 and Comparativeexamples 12-1 to 12-3 were examined, the results shown in Table 12 wereobtained.

TABLE 12 Initial Discharge Anode active material layer (Anode material)charge and capacity Anode active material Covering particles dischargeretention Laminated Forming Ratio efficiency ratio film type Type methodType (wt %) (%) (%) Example 12-1 SnCoC Coating K₂CO₃ 1 83 94.7 methodExample 12-2 Si Electron 85 90.2 beam evaporation method Example 12-3Sputtering 85 91.3 method Comparative SnCoC Coating — — 71 89.7 example12-1 method Comparative Si Electron 75 86.3 example 12-2 beamevaporation method Comparative Sputtering 74 88.7 example 12-3 method

As shown in Table 12, in Examples 12-1 to 12-3 in which the plurality ofcovering particles 222 were formed, the initial charge and dischargeefficiency and the discharge capacity retention ratio were highercompared to those of Comparative examples 12-1 to 12-3 in which theplurality of covering particles 222 were not formed. Accordingly, in thesecondary battery of an embodiment, it was confirmed that the input andoutput characteristics were also secured and the cycle characteristicswere also improved when the battery structure was changed in the casethat the SnCoC-containing material or silicon was used as an anodeactive material.

As evidenced by the results of the foregoing Table 1 to Table 12 andFIG. 10 and FIG. 12, in the secondary battery of an embodiment, it wasconfirmed that the input and output characteristics were secured and thecycle characteristics were improved irrespective of the type, thecomposition, the forming method, the battery structure and the like ofthe anode active material when the plurality of covering particlescontaining at least one of the alkali metal salt and the alkali earthmetal salt were formed on the surface of the anode active material inthe case that the carbon material or the material containing at leastone of the metal element and the metalloid element was contained as ananode active material capable of intercalating and deintercalating theelectrode reactant.

The present application has been described with reference to theembodiments and the examples. However, the present application is notlimited to the aspects described in the foregoing embodiments and theforegoing examples, and various modifications may be made. For example,the anode material and the anode of the present application are notnecessarily used for the battery, but may be used for an electrochemicaldevice other than the battery. As other application, for example, acapacitor or the like is cited.

Further, in the foregoing embodiments and the foregoing examples, thedescriptions have been given of the case using the electrolytic solutionor the gel electrolyte in which the electrolytic solution is held by thepolymer compound as an electrolyte. However, other type of electrolytemay be used. As other type of electrolyte, for example, a mixtureobtained by mixing an ion conductive inorganic compound such as ionconductive ceramics, ion conductive glass, and ionic crystal and anelectrolytic solution; a mixture obtained by mixing other inorganiccompound and an electrolytic solution; a mixture of the foregoinginorganic compound and a gel electrolyte or the like is cited.

Further, in the foregoing embodiments and the foregoing examples, thedescriptions have been given of the lithium ion secondary battery inwhich the anode capacity is expressed based on intercalation anddeintercalation of lithium as a battery type. However, the battery ofthe present application is not limited thereto. The present applicationis similarly applicable to a secondary battery in which the anodecapacity includes the capacity by intercalation and deintercalation oflithium and the capacity by precipitation and dissolution of lithium,and the anode capacity is expressed as the sum of these capacities, bysetting the charge capacity of the anode active material capable ofintercalating and deintercalating lithium to a smaller value than thatof the charge capacity of the cathode active material.

Further, in the foregoing embodiments and the foregoing examples, thedescriptions have been given with the specific examples of the secondarybatteries having a battery structure of cylindrical type and laminatedfilm type, and with the specific example of the battery in which thebattery element has the spirally wound structure. However, the presentapplication is similarly applicable to a battery having other structuresuch as a square type battery, a coin type battery, and a button typebattery, or a battery in which the battery element has other structuresuch as a lamination structure. The battery of the present applicationis similarly applicable to other type of battery such as a primarybattery in addition to the secondary battery.

Further, in the foregoing embodiments and the foregoing examples, thedescription has been given of the case using lithium as an electrodereactant. However, as an electrode reactant, other Group 1 A elementsuch as sodium and potassium, a Group 2A element such as magnesium andcalcium, or other light metal such as aluminum may be used. In thesecases, the material described in the foregoing embodiments may be usedas an anode active material as well.

Further, in the foregoing embodiments and the foregoing examples, forthe ratio of the plurality of covering particles to the anode activematerial in the anode material, the anode or the battery of anembodiment, the numerical value range thereof derived from the resultsof the examples has been described as the appropriate range. However,such a description does not totally eliminate the possibility that theratio may be out of the foregoing range. That is, the foregoingdesirable appropriate range is the range particularly preferable forobtaining the effects of the present application. Therefore, as long aseffects may be obtained, the ratio may be out of the foregoing range insome degrees. The same is applied to the thickness, the volume densityand the like of the anode active material layer in addition to theforegoing ratio.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. An anode comprising: an anodeactive material layer on an anode current collector, wherein the anodeactive material layer includes an anode active material capable ofintercalating and deintercalating an electrode reactant, wherein athickness of the anode active material layer ranges from 60 μm to 120μm, and wherein the anode active material includes a carbon material andat least part of a surface is covered by a covering, the coveringincluding at least one of an alkali metal salt and an alkali earth metalsalt.
 2. The anode according to claim 1, wherein the alkali metal saltis at least one selected from the group consisting of lithium chloride,sodium chloride, potassium chloride, lithium sulfate, sodium sulfate,potassium sulfate, and mixtures thereof, and the alkali earth metal saltis at least one of magnesium carbonate, calcium carbonate, and mixturesthereof.
 3. The anode according to claim 1, wherein the carbon materialis natural graphite.
 4. The anode according to claim 1, wherein a volumedensity of the anode active material layer ranges from 1.70 g/cm³ to1.95 g/cm³.
 5. The anode according to claim 1, wherein the anode activematerial includes a material containing at least one of a metal elementand a metalloid element.
 6. The anode according to claim 5, wherein thematerial containing at least one of the metal element and the metalloidelement is at least one selected from the group consisting of a simplesubstance of silicon, an alloy of silicon, a compound of silicon, asimple substance of tin, an alloy of tin, and a compound of tin.
 7. Theanode according to claim 5, wherein the material containing at least oneof the metal element and the metalloid element is a material containingtin as a first element, at least one selected from the group consistingof cobalt, iron, magnesium, titanium, vanadium, chromium, manganese,nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, silver,indium, cerium, hafnium, tantalum, tungsten, bismuth, and silicon as asecond element, and at least one selected from the group consisting ofboron, carbon, aluminum, and phosphorus as a third element.
 8. A batterycomprising: a cathode; an anode; and an electrolytic solution, whereinthe anode includes an anode active material layer on an anode currentcollector, wherein the anode active material layer includes an anodeactive material capable of intercalating and deintercalating anelectrode reactant, wherein a thickness of the anode active materiallayer ranges from 60 μm to 120 μm, and wherein the anode active materialincludes a carbon material and at least part of a surface is covered bya covering, the covering including at least one of an alkali metal saltand an alkali earth metal salt.
 9. The battery according to claim 8,wherein the alkali metal salt is at least one selected from the groupconsisting of lithium chloride, sodium chloride, potassium chloride,lithium sulfate, sodium sulfate, potassium sulfate, and mixturesthereof, and the alkali earth metal salt is at least one of magnesiumcarbonate, calcium carbonate, and mixtures thereof.
 10. The batteryaccording to claim 8, wherein the carbon material is natural graphite.11. The battery according to claim 8, wherein a volume density of theanode active material layer is in the range from 1.70 g/cm³ to 1.95g/cm³.
 12. The battery according to claim 8, wherein the anode activematerial includes a material containing at least one of a metal elementand a metalloid element.
 13. The battery according to claim 12, whereinthe material containing at least one of the metal element and themetalloid element is at least one selected from the group consisting ofa simple substance of silicon, an alloy of silicon, a compound ofsilicon, a simple substance of tin, an alloy of tin, and a compound oftin.
 14. The battery according to claim 12, wherein the materialcontaining at least one of the metal element and the metalloid elementis a material containing tin as a first element, at least one selectedfrom the group consisting of cobalt, iron, magnesium, titanium,vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium,niobium, molybdenum, silver, indium, cerium, hafnium, tantalum,tungsten, bismuth, and silicon as a second element, and at least oneselected from the group consisting of boron, carbon, aluminum, andphosphorus as a third element.